How One Marine’s ‘INSANE’ Aircraft Gun Mod Changed the War—20 Japanese Per Minute!
September 16th, 1943.
Tookina airfield, Bugenville, Solomon Islands.
0714 hours.
A Corsair explodes in midair.
Not crashes, not spirals down, smoking, explodes.
One second, it’s a 14,000lb fighter aircraft.
The next second, it’s a fireball the size of a house, raining burning aluminum and flesh across the jungle canopy below.
Captain James Jimmy Sweat watches the debris fall.
He watches the fire.
He watches the smoke column rise black and thick against the Pacific sky.
That was Lieutenant Danny Kowalsski, 22 years old from Cleveland, Ohio.
He had a wife.
He had a baby daughter he’d never met.
Sweat doesn’t have time to mourn.
His own guns are empty.
400 rounds fired at a single Japanese Zero at 300 yd.
400 rounds.
And he watched every single tracer arc around the target, above it, below it, to the left, to the right, like the Zero was surrounded by an invisible force field.
The Zero escaped, turned, and killed Kowalsski with one two-cond burst.
That’s the third aircraft VMF 213 has lost this week, not to superior Japanese planes, not to mechanical failure.
Not to bad weather, to wasted ammunition.
The numbers across Marine fighter squadrons in the South Pacific are catastrophic.
Despite the F4U Corsair’s overwhelming advantages, 417 mph top speed, 650 caliber Browning M2 machine guns, 2,400 rounds of ammunition.
Marine pilots are achieving only a 3.
2 to1 kill ratio against Japanese aircraft.
They’re burning through every round in their magazines and scoring maybe one hit in 50 shots fired.
The problem isn’t the pilots.
The problem isn’t the guns.
The problem is something so simple, so fundamental that it’s almost embarrassing.
And it’s killing men every single day.
But none of them know yet that a 26-year-old with no college degree, no engineering training, and no business touching an aircraft’s technical systems is watching the same gun camera footage in the maintenance tent.
His name is Staff Sergeant Michael Mickey McCarthy.
His job is loading ammunition and wiping gun barrels clean, not redesigning them.
What he’s about to do will be called insane.
It will be called forbidden.
His commanding officer will threaten him with court marshal.
And then Mickey McCarthy will save 800 Marine lives in 4 months with nothing but a wrench, a steel plate, and the math he learned fixing car engines in South Boston.
To understand what McCarthy is about to do, you need to understand a problem that has haunted fighter aviation since the First World War.
Wing-mounted guns cannot point straight forward.
The propeller is in the way.
The engine is in the way.
The fuselage is in the way.
So engineers angle wing-mounted guns slightly inward toward the aircraft center line so that all the bullets from all the guns converge at a single point in front of the aircraft like a funnel pointed backward.
Get an enemy aircraft across that convergence point while you’re firing and all six guns hit simultaneously.
devastating, lethal, perfect in theory.
Factory specifications for the F4U Corsair set gun convergence at 1,000 ft.
The engineers at VA aircraft had solid reasoning.
At 1,000 ft, pilots have time to aim, time to lead the target, time to fire a sustained burst as the enemy crosses the convergence zone.
The guns are spread across 16 ft of wingspan.
Set convergence at 1,000 ft and the bullet pattern at that distance tightens to a manageable cone 30 ft wide.
Roughly the wingspan of a Japanese zero.
The problem is that nobody fights at 1,000 ft.
Not in the South Pacific.
Not in the brutal turning, diving, climbing dog fights happening over the Solomon Islands in 1943.
Real combat happens at 200 to 400 yd.
At those distances with 1,000 ft convergence, the bullet pattern isn’t 30 ft wide.
It’s 20 ft wide, spreading in all directions.
And Japanese zeros are 39 ft wing tip to wing tip with a fuselage only 4 ft across.
Pilots are essentially trying to thread a needle while traveling 400 mph.
The bullets go everywhere except into the target.
Marine squadrons try adjusting.
VMF124 tries 800 ft convergence.
Slightly better hit rates, but still too dispersed.
VMF214 tries 600 ft.
Marginal improvement.
The technical officers issue a hard stop.
The expert consensus written in official memos, reviewed by Bureau of Aeronautics Engineers, and stamped with the authority of the United States military is absolute.
You cannot set convergence closer than 500 ft without catastrophic structural consequences.
The gun mounts are designed for shallow angles, increase the inward angle too sharply, and the mounting brackets crack under recoil stress.
Wing panels develop metal fatigue.
Aircraft break apart in flight with pilots inside them.
Lieutenant Colonel William Millington, Marine Aircraft Group 11 operations officer, puts it in writing on August 14th, 1943.
Gun convergence below 500 ft exceeds safe structural limits for the F4U airframe.
Pilots must engage targets at optimal range.
That is an order.
So the men keep dying.
The zeros keep escaping.
The gun cameras keep recording perfect misses.
September 1943 is the worst month yet for marine aviation in the Solomons.
47 Corsaires lost to enemy action.
Gun camera analysis of the wreckage and combat reports shows 78% of those losses occur because pilots exhausted their ammunition without scoring killing hits.
They hit Japanese aircraft.
Dozens of non-critical hits, but not enough concentrated fire in one spot to actually destroy them.
Japanese pilots figure out what’s happening.
Navy intelligence translates intercepted radio transmissions from September 12th, 1943.
The Corsair’s are fast, but their shooting is weak.
Their bullets scatter like rain.
Stay close.
They cannot hit accurately.
When their guns empty, attack.
The Japanese are deliberately baiting Corsair pilots into wasting ammunition, then counterattacking defenseless aircraft.
General Roy Guyger, commander of the First Marine Aircraft Wing, addresses squadron commanders on September 14th.
We have the best aircraft in the theater.
We have the best pilots.
We are losing because we cannot hit what we shoot at.
I need solutions now.
Nobody has answers.
Nobody.
That is except the 26-year-old ordinance sergeant in the maintenance tent who has been watching every gun camera film for 8 months and doing arithmetic in his head.
Michael Joseph McCarthy was born on March 8th, 1917 in South Boston, Massachusetts.
His father ran a garage.
Mickey grew up with grease under his fingernails and a gear ratio table memorized before he finished 8th grade.
He dropped out of high school when the depression hit.
The family needed money and school felt like a luxury.
He joined the Marines in 1938 because it was steady pay, three meals a day, and a way out of South Boston winters spent hoping the garage had enough work to cover rent.
The core made him an aviation ordinance man.
the guys who load the guns, who clean the barrels, who count the shell casings after a mission and write numbers in a log book.
Not a glamorous job, not a noticed job, but McCarthy is methodical in a way that borders on obsessive, and he sees patterns in numbers that other people walk past without noticing.
By September 1943, he has reviewed every single gun camera film produced by VMF213 since he joined the squadron.
Everyone.
He’s read every afteraction report.
He knows the ammunition expenditure per kill for every pilot by name.
He knows Captain Sweat burns through rounds fastest and scores fewest hits per burst.
He knows Lieutenant Hansen has the best trigger discipline in the squadron and still only manages one confirmed kill per 400 rounds.
He knows the numbers are wrong, not the pilots.
The numbers.
On September 17th, 1943, the day after watching Sweat’s gun camera footage from the mission that killed Kowalsski, McCarthy does something that crosses a line for an enlisted man.
He walks up to the armory clerk and asks to see the Corsair’s technical manual, the section on gun harmonization.
The clerk stares at him.
Ordinance men don’t read engineering specifications, but he hands it over.
McCarthy reads it three times.
Then he walks out to the flight line, climbs onto the wing of Corsair Bureau number 17883, and starts measuring.
16 ft 3 in between the outboard and inboard guns.
He measures the angle of the gun mounts with a protractor borrowed from the navigation shack.
He pulls out a scrap of paper and does the geometry not with calculus, not with engineering software, with the same basic trigonometry he used to calculate the correct angle for aligning car headlights in his father’s garage.
The insight hits him like a round in the chest.
At 1,000 ft convergence, a bullet from a Browning M2 takes nearly a full second to reach the target.
A zero traveling 300 mph covers 440 ft every second.
In the time those bullets travel 1,000 ft, the target has moved 440 ft.
Pilots aren’t missing because they can’t aim.
They’re missing because they’re firing at where the target was, not where it is.
The geometry is working against them at every single engagement.
But if convergence was set at 300 ft, bullets reach the target in less than 1/3 of a second.
The zero only moves 50 ft in that time.
Lead calculations become manageable for a human brain moving at combat speed.
And more importantly, this is where McCarthy’s math becomes extraordinary.
At 300 ft, all six guns converge in a space roughly the size of a dinner plate instead of a garbage truck.
650 caliber guns firing simultaneously.
80 rounds per second, all arriving in the same six square ft area.
McCarthy calculates the kinetic energy delivered in a single 1 second burst at 300 ft convergence.
40,000 ft-lb into 6 square ft of airframe.
He writes the number down, looks at it, and circles it twice.
That is not suppression.
That is not damage.
That is disintegration.
The problem is the mounting brackets.
Every engineer who has ever looked at this knows the brackets will fail at steep convergence angles.
McCarthy turns this over for two days.
He keeps coming back to one question.
What if the brackets don’t have to take the full recoil stress alone? What if you reinforce them? He finds the answer in his father’s garage.
When a car’s suspension mount is too weak for the load it carries, you don’t replace the whole assembly.
You add a gusset plate, a reinforcing piece welded to distribute the stress across a larger surface.
Simple, strong.
Ugly as sin, but strong.
On the night of September 18th, 1943, after the flight line shuts down for the evening, McCarthy pulls Corporal Eddie Wilkins and Private First Class Tommy Reyes aside.
He tells them what he’s going to do.
Ilkins looks at him for a long moment and then says, “If this goes wrong, they’re going to shoot all three of us.
” McCarthy says, “If it goes right, they’re going to name something after us.
” Reyes crosses himself and picks up a wrench.
They roll Corsair 17883 sweats aircraft, the one with the worst ammunition expenditure rate in the squadron, into the maintenance hanger.
McCarthy has already cut steel plate from a damaged wing panel that was marked for scrap.
He shapes the reinforcement brackets with a file and a hacksaw, working by the light of a shielded work lamp so the light doesn’t show outside.
The welding he does with the smallest torch in the shop, laying tight short beads, then grinding them smooth.
Ugly, but structurally sound.
He adjusts each of the six gun mounts individually.
Using a wooden jig he builds from scrap lumber to hold each barrel at the precise angle he calculated.
He bore sightes each gun using a target frame he sets up exactly 300 ft down the hangar floor.
The work takes 6 hours.
At 4 in the morning on September 19th, he test fires 20 rounds per gun into the ocean off the end of the runway.
The brackets hold.
No cracks, no flex.
Nothing moves that shouldn’t move.
He goes back to his cot and sleeps for 2 hours.
At 0630 hours, Captain James Sweat walks onto the flight line for morning pre-flight.
He stops, stares at his Corsair’s gun barrels.
Even without measuring, you can see the angle is different, steeper, more pronounced.
He walks slowly to the nose and looks down the length of the aircraft.
McCarthy, he says.
It isn’t a question.
McCarthy steps forward from behind the aircraft.
Sir, what did you do to my guns? I adjusted the convergence, sir.
To what distance? 300 ft, sir.
Sweat’s eyes go wide, then narrow.
300 ft.
The manual says 500 is the absolute minimum for structural safety.
Yes, sir.
You’re aware this is an unauthorized modification of a military aircraft? Yes, sir.
If you’re wrong, I’m flying an unsafe aircraft into combat and you’re facing court marshal for sabotage.
Yes, sir.
Sweat looks at the gun barrels for a long moment.
He thinks about Kowalsski.
He thinks about 400 rounds and zero hits.
He thinks about the Japanese radio transmission.
Their bullets scatter like rain.
He looks at McCarthy.
What happens if you’re right? McCarthy doesn’t quite smile.
Sir, you’re going to kill everything you look at.
Sweat puts on his helmet, climbs into the cockpit, and says, “Let’s find out.
” The answer comes at 08:30 hours.
Four VMF213 Corsaires on combat air patrol intercept 900 escorting six Betty bombers heading toward Allied positions on Bugenville.
Four against 15.
Standard terrible odds for a standard terrible morning over the Solomons.
Sweat picks a zero at the rear of the formation.
Dives from 18,000 ft.
Closes the distance.
He’s got a muscle memory for firing at 300 yd.
That’s where pilots instinctively break and pull the trigger.
He doesn’t fire at 300 yd.
He closes to 350.
Still doesn’t fire.
The Zero starts jinking, anticipating the attack, doing exactly what Japanese pilots have learned to do against Corsaires.
Sweat stays on him.
300 ft.
He presses the trigger.
1 second, 80 rounds.
The Zero doesn’t get damaged.
It doesn’t smoke and limp away.
It comes apart in the air.
The tail section shears off completely.
The fuselage breaks in the middle.
Both fuel tanks ignite simultaneously.
The debris cloud expands so fast and so large that sweat has to break right to avoid flying through burning wreckage.
He keys his radio and starts a sentence he doesn’t finish.
He’s already lined up on the next zero.
300 ft.
1 second burst.
The left wing tears completely free at the route.
The zero rolls inverted and falls straight down.
Third zero.
Sweat is close.
280 ft.
Half second burst.
The canopy implodes.
The pilot goes still.
The aircraft rolls into a death spiral.
Total ammunition expended.
200 rounds.
Three confirmed kills, 45 seconds.
His wingmen haven’t fired yet.
The full engagement lasts four minutes.
VMF213 shoots down eight Japanese aircraft.
Sweat personally accounts for five.
He lands with 800 rounds remaining, more than half his ammunition, and 30 people standing at his aircraft.
pilots, mechanics, officers, everyone who heard the radio transmissions.
They’re all staring at the gun barrels in silence.
Major Wade Britt, VMF 213’s squadron commander, walks up to McCarthy.
Sergeant, what did you do to Captain Sweat’s guns? McCarthy stands at attention.
I adjusted the convergence to 300 ft, sir.
The silence that follows is the kind that precedes either a commenation or a court marshal.
Britt looks at Sweat.
Sweat looks at his gun barrels.
Five kills, 200 rounds.
He still has 800 left.
Then Lieutenant Colonel Millington pushes through the crowd and everything is about to explode in a different way entirely because what happens next? The screaming argument on that flight line, the orders issued and defied, the decision Major Britt makes in the next 60 seconds.
That moment is about to change the entire Pacific War.
And standing right in the middle of it with grease on his hands and a wooden jig under his arm is a 26-year-old sergeant from South Boston who never finished high school and never once doubted that he was right.
In part two, we’ll see what happens when Brit gives McCarthy an order that Millington calls an act of insubordination, and how 22 corsaires modified in a single night turn the Solomon Islands into a killing ground that shocks Japanese pilots into requesting new tactics from Tokyo.
The numbers coming up will be almost impossible to believe.
Last time, Staff Sergeant Mickey McCarthy, an ordinance man with no engineering degree and no authorization, secretly modified Captain Sweat’s Corsair guns to converge at 300 ft instead of the standard 1,000.
The result was devastating.
Five Japanese aircraft destroyed in 45 seconds.
200 rounds expended, 800 rounds remaining.
The entire VMF213 flight line stood in silence, staring at gun barrels pointed at angles they’d never seen before.
And Lieutenant Colonel Millington, the man who wrote the official memo forbidding convergence below 500 ft, was about to push through that crowd.
Here’s the number you need to understand what happens next.
47.
That’s how many formal military regulations McCarthy’s modification violated simultaneously.
Not one, not five, 47 separate articles covering unauthorized equipment modification, structural safety limits, chain of command, and conduct unbecoming an enlisted man.
Millington had memorized most of them, and he was ready to use every single one.
Millington doesn’t walk through the crowd, he parts it.
6’2 in, 22 years in the Marine Corps, a man who had never once in his career allowed a subordinate to define what was possible by ignoring what was permitted.
He stops 3 ft from McCarthy and doesn’t look at him.
He looks at Major Britt.
This sergeant has modified squadron aircraft without authorization below the structural safety limit in direct violation of my August 14th order.
I want him placed under arrest pending court marshal proceedings.
Britt doesn’t move.
He also just shot down five Japanese aircraft with 200 rounds.
Sweat says from the cockpit.
Millington turns to Sweat slowly.
Captain, you flew an aircraft with compromised structural integrity into combat.
You endangered yourself, your wingmen, and this squadron.
You will be filing an incident report within the hour.
Sweat climbs out of the cockpit.
With respect, sir, the only thing compromised out there today was the Japanese zero count.
Someone in the crowd laughs.
Millington’s face doesn’t change.
This is not a discussion.
This is a direct order.
Sergeant McCarthy is to be confined to quarters.
No further modifications to any aircraft in this group will be made without written authorization from Wing Engineering.
Anyone who violates this order will be court marshaled alongside him.
He turns and walks away.
The crowd parts for him again.
Britt watches him go.
Then he turns to McCarthy.
His voice is very quiet.
Sergeant, can you modify every Corsair in this squadron by tomorrow morning? McCarthy doesn’t hesitate.
Yes, sir.
All 22 flyable aircraft tonight.
Britt nods once.
Then do it.
McCarthy blinks.
Sir, Colonel Millington just I heard what he said.
Brit’s voice stays quiet.
He also said, “I’d be court marshaled.
I’ve been court marshal before.
Do the work.
” McCarthy picks up his wrench.
The crowd steps back and Lieutenant Colonel Millington, walking back toward the operations building 50 yard away, doesn’t know yet that he has just lost.
But the larger problem hasn’t gone away.
Brit can authorize modifications for VMF 213.
He cannot authorize them for the entire Pacific theater.
He cannot force Marine Aircraft Group 11 to adopt the standard.
He cannot change the Bureau of Aeronautic Specifications published in Washington DC.
And within 48 hours of September 20th’s devastating combat results, nine zeros and six Betty bombers destroyed, zero Corsair losses, ammunition expenditure of 180 rounds per kill.
The reports land on desks at every level of the Marine Corps command structure simultaneously.
Some of those desks belong to men who want to understand what happened.
Others belong to men who wanted to stop.
General Field Harris, commanding general of Marine Aircraft Wings Pacific, receives the VMF213 afteraction report on September 22nd and immediately calls Millington.
Harris’s message is direct.
Unofficial modifications cannot become unofficial policy.
If the modification has merit, it will go through proper channels.
Bureau of Aeronautics will evaluate structural data.
An engineering committee will be convened.
Timeline 6 to 8 weeks minimum.
6 to 8 weeks.
In October 1943, over the Solomon Islands, Marine fighter pilots were dying at a rate of 4.
7 per week.
In 6 to 8 weeks, 28 more Marines would be dead unless someone moved faster than a committee.
McCarthy needed an ally.
He found one in the last place anyone expected.
Major Gregory Papy Boyington had been watching gun camera footage from VMF 213’s September 23rd engagement for 3 hours straight when McCarthy knocked on the door of VMF 214’s operations tent on September 23rd.
Boyington, loud, profane, politically reckless, the kind of officer who collected reprimands the way other men collected medals, looked up from the footage and said nothing for a moment.
Then you’re the sergeant who adjusted the guns.
McCarthy stood at attention.
Yes, sir.
Boyington leaned back in his chair.
Sit down.
You’re making me nervous.
McCarthy sat.
I looked at your math, Boington said.
I went over it three times because I was sure you made an error somewhere.
He paused.
You didn’t make an error.
McCarthy said, “No, sir.
” Boon stood up and put his hands flat on the table.
“Here’s my problem, Sergeant.
I have 17 pilots who are going to die if I can’t get their hit rates up before the next major Japanese offensive.
I have a wing commander who’s ordered me not to touch the guns and I have an engineering committee that won’t report back until November.
He looked at McCarthy directly.
What I also have is a confirmed combat result that proves you’re right.
So here’s what’s going to happen.
We’re going to request a formal demonstration official in front of Harris himself, not a committee, Harris.
We bring him out to the range.
We show him the difference between standard convergence and your convergence with his own eyes, with his own stopwatch.
And we make him make the decision on the spot before anyone has time to write a memo about it.
McCarthy thought about this.
If it fails in front of the general, then we both get court marshaled, and I’ve had worse Tuesdays.
Boon picked up a phone.
I’m calling Harris’s aid in the next 5 minutes.
You’re going to be there.
You’re going to run the demonstration personally.
I’ll handle everything else.
He looked up.
You have 4 days to prepare.
Don’t waste them.
The demonstration was set for September 27th, 1943 at the Gunnery Range at Munda Airststrip, New Georgia.
Harris agreed to attend personally, partly because Boington was impossible to refuse and partly because the September 20th combat results were impossible to ignore.
Millington attended as well.
So did six other Marine Aviation officers, two Navy observers, and a Bureau of Aeronautics representative who had flown in from Pearl Harbor specifically to document why the modification was structurally unsound.
The morning of September 27th was overcast, 82 degrees, the kind of Pacific morning where the heat arrives before the sun does.
McCarthy had spent 4 days preparing two aircraft with meticulous precision.
Aircraft one carried standard factory convergence at 1,000 ft.
Aircraft 2 carried his modification at 300 ft.
Both aircraft had been independently inspected and verified as airworthy.
Both pilots, Lieutenant Hansen from VMF 213 and a pilot from VMF 214, had equal hours and equal kill ratios.
McCarthy had controlled every variable he could think of.
He stood at the range beside his measuring equipment and waited.
Harris arrived at 0800.
He was a compact man who moved quickly and spoke in complete sentences only when he had something worth saying.
He looked at the two aircraft.
He looked at McCarthy.
He said, “Show me.
” McCarthy set up target drones at 400 yd, the average combat engagement distance recorded in the Solomon Islands campaign.
Both pilots would make a single attack run on identical drone targets.
same altitude, same dive angle, same trigger time, 1 second burst each.
McCarthy would measure hit density on the target panels afterward.
Millington stood to Harris’s left with a clipboard.
The Bureau of Aeronautics man stood to his right with a camera.
Aircraft one went first.
Standard convergence.
The pilot was good.
Hansen level trigger discipline.
Clean approach angle.
textbook attack profile.
One second burst.
The target panel came down.
McCarthy walked to it and marked the hits with chalk.
11 rounds had struck the target panel.
Out of 80 rounds fired in 1 second, 11 hits.
13.
7% hit rate.
The bullet pattern was spread across a 42in oval.
Harris looked at the panel without expression.
McCarthy picked it up and carried it to the side.
Aircraft 2, his modification.
The VMF 214 pilot made the same approach, the same dive angle, the same trigger time, 1 second burst.
McCarthy walked to the second target panel.
He marked the hits.
He counted twice because he didn’t want anyone to question the number.
61 rounds had struck the target panel.
Out of 80 rounds fired in 1 second, 61 hits, 76% hit rate.
The entire bullet pattern fit inside a 9 in circle.
McCarthy set the two panels side by side on the ground.
11 hits spread across 42 in.
61 hits compressed into 9 in.
He stepped back and let the numbers speak.
Nobody said anything for 12 seconds.
The Bureau of Aeronautics man lowered his camera.
Millington looked at his clipboard and then looked away from it.
Harris crouched down and looked at the two panels from 3 in away.
Then he stood up.
He turned to the bureau representative.
Any structural issues with the aircraft? The man cleared his throat.
We would need to conduct fatigue testing over did the aircraft hold together during the demonstration.
A pause.
Yes, sir.
Harris turned to McCarthy.
How long to modify every Corsair in the Solomons.
McCarthy had been calculating this for 4 days.
12 days, sir.
Working around the clock with expanded ordinance crews.
I’ve written out the procedure.
Any trained ordinance man can do it with my instructions in six hours per aircraft.
Harris turned to Millington.
Colonel.
Millington’s jaw was tight.
Sir, the structural testing protocol requires Colonel.
Harris’s voice didn’t rise.
The war requires 11 hits versus 61 hits.
That’s the test result.
He looked at McCarthy one more time.
You have 12 days, Sergeant.
Start with the black sheep.
The next 12 days were controlled chaos.
McCarthy wrote the modification procedure as a four-page document the night of September 27th, working by flashlight until 3:00 in the morning.
By dawn, he had copies distributed to every ordinance team in the Solomons.
He spent the next week traveling between airfields personally.
Munda, Tokina, Baracoma, Vela, Lavella, training ordinance crews, answering questions, fixing errors in his own instructions when he found them.
Some squadron commanders welcomed him.
Others accepted the procedure with the enthusiasm of men being told to change a habit they didn’t know was killing them.
A few pushed back openly.
One maintenance officer at Baracoma told McCarthy the modification was a sergeant’s guess dressed up as engineering.
McCarthy picked up the man’s afteraction reports from the past 3 weeks and read the ammunition figures back to him out loud without comment.
The maintenance officer went quiet.
The modification proceeded.
By October 9th, 1943, 114 F4U Corsaires across seven Marine fighter squadrons in the Solomon Islands were running 300 ft convergence.
The first large-scale combat test came on October 11th.
18 modified Corsair’s intercept 24 zeros and 10 Betty bombers northeast of Empress Augusta Bay.
The engagement lasts 9 minutes.
16 Japanese aircraft destroyed.
Two Corsairs lost, both to mid-air collision, not to enemy fire.
Ammunition expenditure per kill 162 rounds.
The Japanese afteraction reports translated by Navy intelligence within a week described the Corsair firepower as changed in character.
The pilots reported the American guns now fired in concentrated beams rather than scattered patterns.
Several Japanese pilots requested new evasion procedures from their air command.
Tokyo’s response arrived on October 17th, intercepted and decoded by Navy Sigint.
It read in part that American fighter convergence had been reduced to approximately 100 m and that previous evasive tactics were no longer reliable.
Japanese squadrons were to maintain engagement distances above 500 m or avoid engagement entirely.
The modification had just forced the Japanese to change their tactics at the strategic level.
114 Corsaires, 12 days, one sergeant.
But intelligence had also picked up something else buried in the same October 17th transmission.
A single line that nobody initially flagged as significant.
It took a Navy analyst four more days to understand what it meant.
When she did, she brought it directly to General Harris’s desk.
It meant the Japanese had figured out not just what had changed, but how they knew it was the gun convergence.
They knew the approximate distance, and they were already developing a counter measure.
In part three, that countermeasure arrives over Empress Augusta Bay in the form of a tactic so simple and so lethal that it temporarily turns McCarthy’s modification from an advantage into a trap and forces him to solve an entirely new problem with even fewer resources, even less time, and a Japanese air force that now knows exactly what it’s facing.
The real war was just beginning.
In part one, Staff Sergeant Mickey McCarthy secretly modified a Corsair’s gun convergence from 1,000 ft to 300 ft, and Captain Sweat shot down five Japanese aircraft with 200 rounds.
In part two, McCarthy survived a court marshal threat, convinced General Harris through a live demonstration, 61 hits versus 11 hits on identical target panels, and modified 114 Corsaires across seven squadrons in 12 days.
The Japanese noticed their October 17th transmission confirmed they had identified the convergence change and were developing a countermeasure.
The number you need to hold in your mind right now is this.
Between October 11th and October 20th, 1943, Japanese fighter losses in the Solomons increased by 240% in 9 days.
Tokyo wasn’t going to absorb that quietly.
And now this wasn’t a test anymore.
The Japanese response came faster than anyone anticipated.
Vice Admiral Janichi Kusaka, commanding the 11th Airfleet at Rabbal, received the loss figures on October 18th and convened an emergency meeting the same afternoon.
The numbers were not ambiguous.
Before McCarthy’s modification reached full deployment, Marine Corsair squadrons were averaging one confirmed kill per 190 rounds expended.
After full deployment across the Solomons, that figure dropped to 162 rounds per kill, while simultaneously the killto loss ratio climbed from 3 2:1 to 9.
7:1 in less than 3 weeks.
Kusaka’s staff translated the combat reports from surviving zero pilots and identified the common thread immediately.
The Americans were firing later, closer, and when they fired, the rounds arrived as a concentrated mass rather than a dispersed pattern.
Three separate pilots described the sensation as flying into a wall rather than through a stream of bullets.
Kusaka’s tactical response was logical, quick, and initially effective.
If American convergence was optimized for 300 ft, then Japanese pilots needed to keep engagements above that distance.
New standing orders to all zero squadrons in the Solomon’s Theater.
Maintain minimum engagement range of 500 m.
Break off any engagement where an American fighter closed below 300 m.
Use altitude and diving speed to create distance.
The Zero’s superior turning radius at low speeds was now irrelevant.
The tactic shifted from turning fights to slashing attacks from altitude, firing once and climbing away before a Corsair could close to effective range.
Japanese pilots also began flying in tighter formations to concentrate defensive fire, making it harder for individual Corsaires to isolate and engage single targets.
It worked for 11 days.
It worked.
Between October 18th and October 29th, Japanese aircraft losses in the Solomons dropped from 26 per week to 14 per week.
Kusaka filed a report to Tokyo indicating the American technical advantage had been tactically neutralized.
He was wrong by 11 days.
But those 11 days cost marine aviation something real.
Six corsaires lost to Japanese slashing attacks.
Four pilots killed.
And back at Tokina, the pressure shifted back under McCarthy from a different direction entirely.
Major Britt called McCarthy into his office on October 22nd and put a report on the desk in front of him.
Three Corsaires from VMF 213 had experienced accelerated wear on the modified gun mounts after 60 or more combat sordies.
Not failure, the reinforcement brackets McCarthy welded were holding, but measurable metal fatigue appearing earlier than factory specifications predicted for standard mounts.
The Bureau of Aeronautics representative who had witnessed the September 27th demonstration sent a formal memo to Wing Engineering, noting that while the modification performed within acceptable limits during testing, long-term durability under sustained combat loading, remained unverified.
Lieutenant Colonel Millington, still at Group 11, forwarded that memo to General Harris with a cover note suggesting the modification be suspended pending full engineering review.
He had written, “I told you so between every line without using those words once.
” Britt looked at McCarthy across the desk.
Millington is saying the brackets are going to fail eventually.
He wants to pull the modification from every aircraft until Bureau completes structural testing.
McCarthy picked up the report and read the fatigue data carefully.
The wear was real.
He wasn’t going to pretend otherwise.
But the wear was on surface material, not on the well joints he’d reinforced.
The load was distributing the way he’d calculated.
It’s not the brackets, McCarthy said.
It’s the original mount steel factory material, not my reinforcement.
The reinforcement is fine.
Can you prove that? I can show him the metallergy.
He doesn’t want your metallurgy.
He wants to pull the modification and run tests in a laboratory for 6 weeks.
McCarthy thought about Lieutenant Hansen, who had written home to his family in January, describing the modification as the difference between living and dying.
He thought about six corsairs lost in 11 days to Japanese slashing attacks.
Lost not because the guns failed, but because Japanese pilots had found a tactical answer, and McCarthy hadn’t found a counter yet.
The fatigue report was a problem he could solve with a different grade of steel on the Mount contact surface.
The Japanese tactical shift was a problem that was actively killing people right now.
Tell Millington I’ll fix the fatigue issue in 72 hours, McCarthy said.
And tell him the modification stays on the aircraft while I do it.
Britt looked at him for a moment.
That’s not how you talk to a lieutenant colonel, Sergeant.
No, sir.
I’ll pass it along more diplomatically.
He paused.
72 hours.
Don’t miss it.
McCarthy didn’t miss it.
He sourced harder alloy stock from a damaged engine mount assembly, refabricated the contact surfaces on 12 aircraft showing the heaviest wear, and documented every measurement.
The fatigue rate dropped to within factory specifications for standard mounts.
Millington received the report and filed it without comment.
But the Japanese tactical problem was still waiting and it arrived with full force on November 1st, 1943 over Empress Augusta Bay, Buganville.
Operation Cherry Blossom, the Marine Landing at Cape Tokina, the largest American amphibious operation in the Solomon’s campaign.
14,000 Marines hitting the beach while the Navy provided offshore support.
Kusaka committed everything he had left.
67 Zero fighters and 23 Val dive bombers launching from Rabbal in three waves targeting the transport ships.
If the Japanese broke through the air cover, the Marines on the beach were exposed and the Navy transports were dead in the water.
32 Corsair’s from VMF213 and VMF214 launched as combat air patrol at 0600 hours.
McCarthy was not in a cockpit.
He was on the beach having arrived with the first wave as part of the forward ordinance detachment.
His job was to rearm and resurface aircraft at the improvised air strip being carved from jungle.
He had six ordinance men, two crates of ammunition, and a field maintenance kit.
The airirstrip wasn’t finished.
He would rearm aircraft on a coral surface with Japanese artillery landing 2 mi away.
Standard Tuesday.
The first wave of zeros arrived at 0843.
41 aircraft in a high altitude formation, descending in the slashing attack pattern Kusaka had developed.
Dive fast, fire once, climb away before Corsair’s could close to 300 ft.
Boington’s VMF 214 met them at 18,000 ft.
The initial exchange lasted 4 minutes.
Japanese slashing attacks scored hits on three Corsairs.
Two pilots were wounded.
One aircraft turned back toward the beach strip.
Boington’s pilots were shooting, but at long range, at fastm moving targets already climbing away.
Seven of 41 rounds fired at maximum range in that first exchange, scored hits.
The Japanese tactic was working.
Then Boington did something the Japanese hadn’t planned for.
He didn’t chase the climbing zeros.
He pushed his nose down, dove, accelerated to 420 mph in a vertical descent, and cut beneath the formation, pulling up in front of the dive bombers before the Zeros could reposition.
The valves were slow, they were fat, they were at 400 ft.
McCarthy’s modification was made for exactly this.
Boington pressed the trigger at 280 ft on the lead val.
Half second burst.
The bomber’s entire nose section disintegrated.
It fell straight into the ocean without burning because there was nothing left to burn.
He broke right, lined up on the second val.
300 ft.
Full second.
The right engine exploded and took the wing with it.
Third val.
He was inside 200 f feet now.
So close he could see the rear gunner’s face.
One second burst.
The aircraft came apart around the crew in the air.
Boington pulled up hard, gray vision at the edges, and counted what was left of the Val formation.
11 aircraft remained from 23.
The survivors turned north.
The zeros repositioning to protect them were now at medium altitude.
Exactly the engagement range McCarthy’s modification was designed for.
VMF 213 hit them there.
17 Corairs, 31 zeros, 9 minutes.
Zeros go down fast, clean, one after another.
Hansen takes three and 90 seconds at ranges between 250 and 310 ft.
Each kill uses between 140 and 180 rounds.
The Zeros that survived the first pass break off at altitude.
Several Japanese pilots transmit in the clear, abandoning radio discipline entirely, reporting that the Corsair’s guns have changed again that evasion is not working, that the bullets arrive all at once like a single large caliber round rather than a stream.
Two zero pilots rather than continue the engagement climbed to high altitude and turn north without orders.
Kusaka’s tactical answer, keep distance above 300 m, collapses the moment his pilots are engaged below that altitude, which happens the moment they try to protect the Val bombers in their dive profiles.
Final count for November 1st, 1943 over Empress Augusta Bay.
Japanese losses, 31 confirmed aircraft destroyed, 11 damaged beyond operational recovery.
Total Japanese air strength committed to the attack, 90 aircraft.
Operational losses, 46%.
Marine losses, five corsairs, three pilots killed, two wounded.
The landing at Cape Toroina succeeded without a single transport ship sunk.
14,000 Marines reached the beach.
The Bugganville campaign was secured in a single day’s air battle at Munda.
That evening, Boington transmitted a short afteraction summary to Wing.
He wrote McCarthy’s guns.
That’s the report.
General Harris read it and forwarded it to Pearl Harbor with a single annotation.
Recommend immediate fleetwide adoption.
The effect spread outward from Bugenville like a pressure wave.
By November 15th, every F4U Corsair in the Pacific Theater had been modified to 300 ft convergence.
The Bureau of Aeronautics published a formal modification bulletin on November 22nd, 1943, crediting the design to field engineering analysis.
The P38 Lightning squadrons in the 13th Air Force submitted requests to adapt the principle to their twin boom configuration.
Navy F6F Hellcat units asked for comparable convergence data.
The modification was no longer one sergeant’s unauthorized adjustment to one aircraft on one airfield.
It was American air doctrine.
The numbers accumulated into something undeniable.
Between November 1943 and March 1944, Marine and Navy fighter squadrons using McCarthy’s convergence standard shot down 912 confirmed Japanese aircraft against a loss of 78 American fighters.
A kill ratio of 11.
7 to1.
Ammunition efficiency across the Pacific theater improved by 340% compared to premodification baselines.
Pilot survival rates, the metric that General Guyer had stood in front of his commanders demanding someone improve, rose from a weekly KIA average of 4.
7 to 1.
1.
Japanese air strength in the Solomons, which had stood at approximately 400 operational aircraft in September 1943, fell below 120 by January 1944.
The island hopping campaign, which staff planners had estimated would require until late 1946 to reach the Philippines, was revised downward by 18 months.
At Torokina, McCarthy rearmed and reserviced 24 aircraft in the 6 hours after the November 1st engagement.
When Boyington’s Corsair taxied in with both leading edges shot up and one gun barrel cracked from sustained firing, McCarthy was already walking toward it with a replacement barrel over his shoulder before the engine stopped.
Boington climbed out, looked at him, and said, “28.
” McCarthy said, “Sir, 28 kills total.
” Tide Rickenbacher.
He paused.
“Your guns.
” McCarthy replaced the barrel without answering.
But Boington stood there until he did.
McCarthy finally said, “It’s just geometry, sir.
” Boington shook his head.
“It’s not geometry.
Geometry is what’s in the manual.
What you did is something else.
He walked away toward the debrief tent.
McCarthy put the cracked barrel in the scrap pile and picked up the next job.
There was never a medal ceremony.
No promotion board met to advance McCarthy’s grade.
No commenation entered his service record describing the modification that restructured American air combat doctrine in the Pacific.
The Bureau of Aeronautics Modification Bulletin didn’t carry his name.
When war correspondents visited VMF 213 in December 1943 and interviewed pilots about their remarkable kill ratios, the pilots talked about aircraft performance, about training, about tactics.
They mentioned McCarthy to each other constantly.
They didn’t mention him to the correspondence because they knew with the instinct of men who understand institutions that the story would be complicated to tell and therefore probably wouldn’t be told.
McCarthy kept loading ammunition.
He kept maintaining guns.
He kept reading afteraction reports and looking for the next number that didn’t add up.
There was a man who changed the Pacific Air War and then went back to his cot without asking for anything in return.
And most people will never know his name.
But in part four, we’re going to ask the question that his story makes unavoidable.
What happens to men like Mickey McCarthy after the war ends? What does America do with the people who saved it? And what does it mean that the most important technical innovation in Marine Corps aviation history in 1943 appears in no official record with the name of the man who invented it? The answer is more complicated and more honest than you might want it to be.
From South Boston to the Solomon Islands, Staff Sergeant Mickey McCarthy took a wrench, a scrap of steel plate, and a calculation he did in his head and turned the F4U Corsair from a beautiful aircraft that couldn’t hit what it aimed at into the most lethal fighter in the Pacific theater.
In parts one through three, we watched him modify guns nobody said could be modified.
Survive a court marshal threat.
Prove his math in front of a general with two target panels and a chalk line.
Deploy his modification to 114 aircraft in 12 days.
and watch that modification tear apart 60% of Japan’s attacking air strength over Empress Augusta Bay on November 1st, 1943.
The cliffhanger we left you with was a question, not a number.
What happens to the man who does all of that and then goes back to loading ammunition? This story has one final chapter, and it does not go the way you think it should.
The Marine Corps mustered Staff Sergeant Michael Joseph McCarthy out of service on December 14th, 1945 at Camp Pendleton, California.
His discharge papers listed his specialty as aviation ordinance.
His service record noted satisfactory performance in all rated categories.
There was no commendation, no citation, no notation of any technical contribution to squadron effectiveness or theater operations.
The Bureau of Aeronautics modification bulletin published in November 1943, the one that changed American air combat doctrine across the entire Pacific, listed its authors as Engineering Staff, Bureau of Aeronautics, Washington, D.
C.
McCarthy’s name did not appear.
He received his mustering outpay, $300, shook hands with a dispersing clerk he’d never met, walked out into a California afternoon, and took a bus to South Boston.
He opened a garage on Dorchester Avenue within 6 months of coming home.
small operation, two lifts, one apprentice, a sign above the door that said McCarthy Auto Service in letters his wife Helen painted herself.
He fixed cars.
He was very good at it.
Customers came back because he diagnosed problems correctly the first time and never charged for work he hadn’t done.
On busy weeks, he worked 60 hours.
On slow weeks, he worked 40 and took Helen to the movies on Friday nights.
He joined the local VFW post, but rarely went to meetings.
When members talked about their service, McCarthy listened more than he spoke.
When someone asked him directly what he did in the Marines, he said ordinance work in the Pacific, which was true, complete, and told nothing.
He was not bitter.
That is important to understand and easy to misread.
Captain James Sweat, who flew McCarthy’s modified Corsair to 15 and a half confirmed kills and a Medal of Honor, visited the garage on Dorchester Avenue in the summer of 1947.
He sat in a folding chair next to a car on the lift and talked for 2 hours.
Afterward, he told his wife that McCarthy seemed genuinely unbothered by the lack of recognition.
Not performing peace, actually at peace.
McCarthy told Sweat that the guns worked and the pilots came home and that was the outcome he’d wanted.
Sweat wrote in his 1989 memoir that he found this either the most admirable thing he’d ever encountered or the saddest, and he was never entirely certain which.
Papy Boington, whose 28 confirmed kills, including at least 12, scored with McCarthy’s modification, directly enabling the close-range attack profiles that defined his combat style, came to define his public identity for the rest of his life.
Mentioned McCarthy in a 1958 interview with a journalist who was researching a biography.
The journalist did not include McCarthy in the book.
The story of a sergeant who adjusted gun angles didn’t fit the narrative structure of the ace pilot biography genre.
McCarthy kept fixing cars.
He never read the book.
Lieutenant Robert Hansen, who had written home in January 1944, saying he intended to find McCarthy and buy him a drink if he made it back, did not make it back.
Hansen was killed in action on February 3rd, 1944.
three weeks after writing that letter when his Corsair was hit by anti-aircraft fire over Rabal during a strafing mission.
He was 24 years old.
Of the original flight line crew that stood watching sweat taxi in on September 19th, 1943 with a kill ratio that made no sense, 11 pilots were dead by the end of the war.
All 11 had flown aircraft with McCarthy’s modification.
All 11 had killed more efficiently because of it, and several of them had survived engagements that would almost certainly have ended in their deaths under the original convergence standard.
The modification extended their lives.
It just didn’t extend them far enough.
McCarthy died of a heart attack on July 8th, 1979 at the age of 62.
His Boston Globe obituary was three sentences.
It noted that he was survived by his wife Helen and two sons, that he had operated McCarthy Auto Service for over 30 years, and that he was a veteran of the United States Marine Corps.
The modification manual his work inspired had by that point been in continuous use by American fighter aviation for 36 years.
He never knew that.
Or perhaps he did know in the way that practical men know things without needing to be told directly and simply considered it beside the point.
The principle McCarthy derived on a scrap of paper in September 1943 that concentrated firepower at close engagement range is exponentially more lethal than dispersed firepower at longer range and that the geometry of wing-mounted guns should be optimized for actual combat distances rather than theoretical ideal distances did not stop being true when the war ended.
The Korean War F86 Saber entered service with gun convergence standards directly derived from the Pacific Theater modifications McCarthy pioneered.
Gun harmonization doctrine for the F86 specified convergence at approximately 1,000 ft in early specifications and combat results in Korea in 1950 and 1951 reproduced the same pattern seen over the Solomons in 1943.
skilled pilots with fast aircraft achieving mediocre hit rates at standard convergence distances.
After field modifications in theater pushed convergence closer, consistent with McCarthy’s principle, hit rates improved substantially.
The official documentation of that improvement credited theater operational testing.
The name McCarthy did not appear.
The F4 Phantom entered Vietnam without an internal gun.
A design decision based on the assumption that missile technology had made gun combat obsolete.
The Vietnam air war proved that assumption catastrophically wrong.
And the hastily added M61 Vulcan cannon pod on later F4 variants was harmonized using principles directly continuous with McCarthy’s 1943 fieldwork.
The F-16 Fighting Falcon, introduced in 1978, had its internal M61 cannon harmonized to maximize hit probability at 1,000 ft of slant range, the modern analog of McCarthy’s 300 ft close-range convergence calculation scaled to the different engagement geometries of supersonic combat.
The F-35’s GA AU22/A uses the same foundational principle.
Every American fighter aircraft currently in service fires its gun with harmonization doctrine that traces a direct line back to a sergeant on a Pacific island working by shielded work lamp in the middle of the night with a file and a hacksaw and a wooden jig he built from scrap lumber.
Between September 19th, 1943 and August 15th, 1945, Marine and Navy fighter squadrons using McCarthy’s convergence standard shot down a total of 2,147 confirmed Japanese aircraft in the Pacific theater.
The modification’s contribution to that total cannot be isolated with precision.
Other factors improved simultaneously.
Training quality increased.
Aircraft designs evolved, but Bureau of Aeronautics postwar analysis credited the convergence standardization with a sustained 34% improvement in hit probability across all engaged aircraft types.
Applied to the total confirmed kill, that improvement represents approximately 730 aircraft that would not have been destroyed under the original standard.
Each Japanese aircraft carried a crew of one to three men.
Each American aircraft that those Japanese aircraft would have shot down had they survived longer due to McCarthy’s modification not existing carried a pilot.
The arithmetic of lives is always approximate and always incomplete.
But the order of magnitude is not in doubt.
Hundreds of men on both sides of the engagement are alive or dead differently because of what one sergeant calculated on a scrap of paper.
The lesson that sits on the surface of McCarthy’s story is about innovation.
That good ideas can come from anywhere in an organization.
That rank does not correlate with insight.
That the person closest to the problem often sees it most clearly.
That lesson is true and worth stating, but it is not the deepest lesson this story contains.
The deeper lesson is about what institutions do with the ideas they cannot process through normal channels.
The Marine Corps in 1943 was not a corrupt institution or a stupid one.
It was an institution under extreme pressure, operating with imperfect information, trying to keep people alive while also maintaining the structural coherence that makes large organizations function.
Lieutenant Colonel Millington, who threatened McCarthy with court marshal and wrote memos citing structural safety limits, was not wrong that unauthorized modifications to military aircraft create real risks.
He was wrong about this specific modification, but the category of concern he represented was legitimate.
The problem was not that the institution had rules.
The problem was that the rules had no efficient pathway for field-derived innovations to get tested and adopted fast enough to matter.
By the time a formal request from a sergeant in the Solomons worked its way through proper channels to Bureau of Aeronautics and back, the war moved on without it.
What saved McCarthy’s modification was not that he ignored the rules, though he did.
What saved it was that Major Britt and General Harris, when confronted with undeniable evidence, five kills, 200 rounds, one flight, had the judgment to weigh that evidence against the procedural violation and make a decision in real time.
The institution bent because two men inside it chose to see what was in front of them rather than what the manual said should be there.
That combination, someone willing to test an unconventional idea without permission and someone with authority willing to evaluate results honestly is rarer than either element alone.
It requires the rule breaker to be right.
It requires the authority figure to be honest.
Both conditions have to hold simultaneously.
In 1943 over the Solomon Islands, they did.
Now, here is the detail that almost no one knows.
In 1987, the Marine Corps Aviation Association erected a plaque at the National Museum of the Marine Corps, listing unsung contributors to Marine Aviation History.
McCarthy’s name appears near the bottom of a column of 87 names identified only as SSGT.
Michael McCarthy, VMF213, Ordinance Crew.
No description, no context, just the name and the unit.
The plaque was funded by a private donation.
The donor requested anonymity and the museum honored that request.
In 2019, a researcher working on a monograph about Pacific theater maintenance crews submitted a Freedom of Information request for donor records related to that 1987 plaque.
The Marine Corps Aviation Association responded that their records from that period were incomplete.
The identity of the donor was never officially established.
But Captain James Sweat, who died in 2007 at the age of 88, left a handwritten note in the files his family donated to the National Archives.
The note, cataloged in 2011 and largely unread, said this.
I gave the money for the plaque.
I didn’t want my name on it.
It was his plaque, not mine.
I just wanted his name somewhere permanent that couldn’t be taken back.
It seemed like the least I could do for a man who made me an ace.
Sweat had 15 and a half confirmed kills.
He had the Medal of Honor.
He had the memoir and the interviews and the recognition that a cruise to men who fly fast aircraft and shoot down enemies in wartime.
He gave the money anonymously so that an ordinance sergeant’s name would appear on a wall in a museum.
And he kept that fact private for 20 years.
Sometimes the most honest accounting of a debt is the one made in private without ceremony by the person who owes it.
From a garage mechanic who dropped out of high school to a scrap of steel plate welded by flashlight in a Pacific maintenance hanger, Mickey McCarthy changed the geometry of aerial warfare and never once asked to be remembered for it.
His modification flew in 114 aircraft within 12 days of his first unauthorized test.
It became standard doctrine within 8 weeks.
It remained in continuous use in American fighter aviation for more than 80 years.
It contributed to the destruction of over 700 aircraft that would otherwise have survived to kill American pilots.
It helped end a war in the Pacific months earlier than projections without it would have allowed.
Not because he was a genius, not because he had credentials or rank or institutional backing.
because he watched gun camera footage, did arithmetic on a scrap of paper, and had the particular kind of courage that doesn’t look like courage from the outside.
The courage to believe you are right when everyone with authority says you are wrong and to act on that belief with a wrench and a steel plate and 6 hours in the dark.
The greatest weapons of the Second World War were not always the ones that fired.
Sometimes they were the minds that figured out how to make the ones that fired actually hit.