The Japanese destroyer Harusami was not a small target. She was 350 ft of hardened steel designed to fight other warships. Her captain, Lieutenant Commander Masau Kamayyama, had fought at Midway and Guadal Canal. He knew the sounds of war. He knew the high-pitched wine of dive bombers and the low rumble of torpedo planes.

He knew how to dodge them. When aircraft attacked you, turned into the torpedoes or broadside to the bombers. It was a calculated game of geometry and speed. But on the morning of November 2nd, 1943, near the harbor of Rabbal, Kamyama faced something that defied the rules of naval warfare. Two twin engine bombers were approaching his ship. They were not at 10,000 ft.

They were not dropping torpedoes. They were flying at 50 ft above the water, lower than the ship’s mast, closing at 280 mph. They looked like standard B-25 Mitchells. Then the nose of the lead plane lit up. There was no machine gun rattle. There was a single massive flash. A fraction of a second later, the Harus army shuddered violently.

A hole the size of a dinner plate appeared in the ship’s steel plating near the waterline. The projectile didn’t stop there. It smashed through the engine room bulkheads, severed high pressure steam lines and detonated deep inside the bowels of the destroyer. Men who were protected by 2 in of armor were instantly killed by shrapnel.

Kamyama’s crew was paralyzed. Aircraft fired 50 caliber bullets. Aircraft dropped bombs. Aircraft did not fire artillery shells. But the B-25s closing in on them was no ordinary bomber. The pilot, Major Ralph Chel of the 38th Bomb Group, was flying a modified B-25G in the nose of his aircraft sat an M4 cannon.

It was the same 75 mm field gun used by Sherman tanks on the ground. It fired a 15lb high explosive shell at 2,000 ft per second. The weapon was 7 ft long and weighed 900 lb. Engineers said it couldn’t be done. They said the recoil would stall the aircraft in midair. They said the vibration would tear the airframe apart.

They said a pilot could never aim a fixed artillery piece at a moving ship while flying at 300 mph just feet above the waves. They were wrong. Major Chel’s gunner handloaded a second shell. The breach slammed shut. Chel fired again. The second round struck the destroyer’s bridge. The impact threw officers across the deck and shattered the fire control systems.

This was not an isolated incident. Across the Southwest Pacific, Japanese supply convoys were being hunted by a weapon they could not understand and could not counter. Japanese naval reports from late 1943 began to speak of a terrifying new phenomenon. They called it sky artillery. American crews called it something else.

They called it the most violent, earshattering, and effective ship killer of the war. This is the story of how a group of renegade mechanics and desperate pilots took a tank gun, shoved it into the nose of a bomber, and changed the physics of air warfare forever. To understand why anyone would bolt a 900lb cannon into an airplane, you have to understand the desperation of 1942.

The war in the Pacific was not about territory. It was about shipping. The Empire of Japan was an island nation with a sprawling perimeter. Every bullet, every gallon of aviation fuel and every bowl of rice for their soldiers on New Guinea or Guadal Canal had to arrive by ship. If the Allies could sink the ships, the Japanese armies would starve.

They would run out of ammunition. They would wither on the vine. But sinking ships was incredibly difficult. General George Kenny, the commander of the fifth air force, arrived in Australia in August 1942. He looked at the numbers and he was appalled. His B7 heavy bombers were flying missions at 25,000 ft. They would drop tons of bombs on Japanese convoys maneuvering in the open ocean.

The result was a mathematical failure. A ship moving at 30 knots could turn and change direction while the bombs were still falling. The hit rate for high altitude bombing against moving ships was less than 1%. Kenny wrote in his diary that his crews were plowing the ocean with expensive explosives. The alternative was low-level torpedo attacks.

But American aerial torpedoes in 1942 were notoriously unreliable. They ran too deep. They failed to explode. They porpused out of the water. And to drop them, a bomber had to fly straight and level for 2 minutes, making them a perfect target for Japanese anti-aircraft gunners. Torpedo squadrons were being slaughtered for almost zero return.

Kenny needed a solution that didn’t exist in the manual. He needed a way to sync ships with the aircraft he had, specifically the B-25 Mitchell and the A20 Havoc. He found his answer in a man who shouldn’t have been in the army at all. Major Paul Irvin Gun was known to everyone as Papy. He was 42 years old, but he looked 60.

He walked with a limp. He had a harsh, grally voice and a reputation for ignoring orders, regulations, and standard operating procedures. Papy Gun was not a West Point graduate. He was a former enlisted naval aviator who had spent years flying civilians around the Philippines before the war. He knew the islands. He knew the weather.

And most importantly, he knew machines. Papy Gun could look at an aircraft engine and tell you why it was coughing without opening the cowling. He didn’t care about aerodynamics theory. He cared about what worked. But Papy Gun also had a personal reason for fighting. When the Japanese invaded the Philippines in December 1941, Gun was away in Australia.

His wife, Strictly Speaking, and his four children were trapped in Manila. They were captured by the Japanese and interned in the Sto. Tomas prison camp. Gun didn’t know if they were alive or dead. He didn’t know if they were being fed or tortured. All he knew was that every Japanese ship he sank was one less ship carrying supplies to the army that held his family.

For Papy Gun, the war wasn’t strategic. It was personal. It was a race against time to kill the enemy before the enemy killed his family. Gun approached General Kenny with a radical idea. He argued that if you couldn’t hit a ship from 30,000 ft, you should get down to 30 ft. He wanted to strip the bombardier and the glass nose out of the B-25 Mitchell.

He wanted to pack the nose with 50 caliber machine guns, four of them, then four more in pods on the side of the fuselage. He wanted to turn a medium bomber into a strafer. The engineers at North American Aviation said it was impossible. They said the weight of the guns in the nose would throw off the center of gravity. They said the recoil of 850 caliber machine guns firing simultaneously would buckle the aluminum skin of the aircraft.

They sent a telegram to General Kenny advising him that the modifications were dangerous and unauthorized. Kenny handed the telegram to Papy Gun. Gun reportedly read it, crumpled it up, and threw it in the trash. He told Kenny General, “I’ve already modified one plane. It flies fine. I’m modifying the rest next week.

” This was the birth of the Commerce Destroyer. Guns modified B-25s went into action in March 1943 at the Battle of the Bismar Sea. The results were catastrophic for the Japanese. Flying at mast head height, gun strafers unleashed a hail of 50 caliber bullets that shredded the decks of Japanese transports.

They killed the bridge crews. They suppressed the anti-aircraft guns. They allowed the bombers to skip bombs across the water like stones. slamming them into the sides of the ships. In 3 days, the Fifth Air Force and the Royal Australian Air Force annihilated a convoy of 16 ships. Thousands of Japanese soldiers drowned. It was a total victory.

But Papy Gun wasn’t satisfied. The 50 caliber machine gun was a terrifying weapon against soft targets. It could kill men. It could ignite fuel drums. It could punch through thin steel. But it couldn’t sink a destroyer. It couldn’t penetrate the heavy armor of a cruiser. To sink a warship, you still needed a bomb. And bombs missed.

Gun wanted a weapon that had the accuracy of a rifle, but the hitting power of a bomb. He wanted to put a hole in a ship below the waterline from a mile away. He didn’t want a machine gun. He wanted a cannon. The idea of mounting a large caliber gun on an aircraft wasn’t entirely new. The P39 Eric Carra had a 37 mm cannon firing through the propeller hub, but a 37 mm shell weighed just over one lb.

It was an annoyance to a ship, not a killer. What gun and the planners at North American Aviation began to discuss was a 75 mm cannon. This was the main gun of the M4 Sherman tank. It fired a shell that weighed 15 lb. The projectile was filled with high explosives that could penetrate 3 in of armor plate and explode inside the target.

But the physics were terrifying. The M4 cannon generated recoil forces of approximately 8,000 lb. When a tank fired the gun, the entire 30 ton vehicle rocked back on its suspension. Papy Gun wanted to mount this weapon in the nose of a B-25 bomber, an aircraft made of aluminum that weighed roughly 20,000 lb empty. The math suggested that firing the gun would be like slamming the aircraft into a brick wall for a fraction of a second.

There were three critical problems that had to be solved and failure in any one of them meant dead crews. First was the mount. You couldn’t just bolt the gun to the floor. The recoil would rip the floor out of the plane. The engineers at North American Aviation, led by the legendary designer Dutch Kindleberger, had to design a cradle that would absorb the shock.

They created a hydro spring recoil mechanism. When the gun fired, the barrel would slide back 21 in against a massive spring and a hydraulic buffer. This system would stretch the recoil impulse over a few milliseconds, reducing the peak force from a shattering blow to a manageable shove. Second was the venting. When a 75 mm shell is fired, it creates a massive cloud of toxic gas and unburned powder in the brereech.

In a tank, you have ventilators. In the tight confines of a B-25 knows that gas would suffocate the crew in seconds. They had to design a complex system of vents and blowers to clear the breach smoke immediately after firing. Third was the airframe itself. The B-25 was a sturdy aircraft known for taking punishment, but the shock wave from the muzzle blast was strong enough to pop rivets and crack the skin of the fuselage.

They had to reinforce the entire nose section with double thick aluminum plating. In the summer of 1942, a prototype was built. It was designated the XB25G. The test pilot for the first firing was Paul Balffor. He took the aircraft up over the California desert. The engineers had warned him that the recoil might cause the plane to stall.

The sudden deceleration could disrupt the air flow over the wings. Balffor climbed to 10,000 ft just in case he needed altitude to recover from a spin. He leveled out. He checked his air speed. He reached for the firing button. On the ground, observers watched through binoculars. They saw a puff of white smoke from the nose of the plane.

A split second later, the sound of the shot reached them. The plane did not fall out of the sky. It did not disintegrate. It shuddered, dipped its nose slightly, and kept flying. Balffor radioed back. It felt like hitting a bump in the road. The bump was actually the aircraft losing about four to 5 mph of air speed instantly.

The recoil was violent, but the B-25 could take it. The concept was proven. North American aviation began production of the B-25G. It carried the 75mm M4 cannon and 250 caliber machine guns in the nose. The cannon had to be loaded manually. The navigator, who now doubled as the canineer, had to crouch in the crawway next to the gun.

The process was crude and dangerous. The canineer would take a 15-lb shell from the rack. He would slide it into the brereech. The brereech block would slam shut. He would shout up to the pilot. The pilot would aim the entire airplane at the target using a simple iron sight or a standard N3B optical sight. He would fire.

The gun would recoil 21 in into the cockpit area, mere inches from the canineer’s face. The empty brass casing, hot enough to burn flesh, would eject onto the floor. The canineer had to kick it out of the way, grab another shell, and reload. In a tank, a good crew could fire 10 rounds a minute. In a bouncing, vibrating bomber flying at 250 mph with the pilot, screaming course corrections and Japanese flack bursting outside a good canineer might get off three or four rounds in a single attack run, but three or four rounds was all they

needed. The first B-25gs arrived in the Pacific in late 1943. They were assigned to units like the 38th bomb group and later the 345th bomb group, the famous air Apaches. The pilots were skeptical. They looked at the massive gun protruding from the nose of their aircraft and shook their heads. It looked ridiculous.

It looked like a cartoon weapon. They nicknamed it the flying telegraph pole. One of the first pilots to test it in combat was Captain Robert Jock Henibri. Henibri was an ace, a man who knew how to handle a B-25. He described the experience of firing the cannon as stopping the airplane in midair.

The cockpit filled with the smell of cordite. The noise was deafening even through flight helmets and headsets. The vibration rattled the instrument panel so hard that gauges became unreadable for a second. But then they saw what it did to a target. On an early training mission against a wreck on a reef, a B-25G pilot fired a single armor piercing round from 2,000 yd away.

The shell hit the rusted Hulk. The explosion was massive. When they flew over to inspect the damage, they found the shell had gone through one side of the ship, torn through the internal bulkheads, and blown a hole out the other side. It was time to hunt. The target was the Japanese barge traffic along the coast of New Guinea.

The Japanese army, starving and cut off, was using hundreds of small motorized barges to move troops and supplies at night. These barges were heavily armed and tough to sink with machine guns. In October 1943, the sky artillery went to work. Lieutenant Edward Higgins of the 38th Bomb Group spotted a 200 ft cargo vessel off the coast.

He initiated his run from 3 mi out. He dropped to 200 ft. At 2,000 yd, he fired. The tracer arc of the 50 caliber machine guns helped him aim, but the cannon was the main event. The first shell fell short, splashing a massive geyser of water in front of the ship. Higgins adjusted the nose up slightly.

The cantoner slammed another round in up Higgins fired. The second shell struck the Japanese ship amid ships. The effect was instantaneous. The vessel didn’t just catch fire, it disintegrated. The 15lb high explosive shell detonated inside the cargo hold, likely igniting ammunition or fuel. The ship broke in half. Higgins later reported, “I’ve never seen a ship disappear that fast.

One minute it was a target, the next minute it was splinters, but the learning curve was steep. The cannon had a flat trajectory, but not that flat. Pilots had to learn to account for the drop of the shell over distance. If they fired too early, the shell would skip off the water. If they fired too late, they risked flying into the explosion of their own target.

And there was another problem. The Japanese shot back. To use the cannon, the pilot had to fly a straight, steady line for 10 to 15 seconds to line up the shot. In aerial combat, flying straight and level for 15 seconds is a suicide note. Japanese anti-aircraft gunners on the destroyers quickly learned that the B-25G had to commit to its run early.

They would wait, hold their fire until the bomber leveled out and then unleash a wall of flack. This led to the second evolution of the sky artillery. The B-25G had a fatal flaw. It only had two 50 caliber machine guns to protect it while the cannon was being reloaded. During the six or 7 seconds it took the canineer to load the next shell.

The plane was vulnerable. The Japanese gunners could aim without being suppressed. Papy Guns saw this problem immediately. He didn’t want fewer guns. He wanted more guns. He sent a message back to North American Aviation. The cannon is good, but we need more machine guns to keep the enemy’s heads down while we reload.

The result was the definitive model, the monster, the B25H. If the G model was an experiment, the H model was a weapon of mass destruction. It kept the 75 mm cannon, but it replaced the heavy M4 field gun with a lighter, specifically designed T13 E1 aviation cannon. It was lighter, but it hit just as hard.

But the real upgrade was the support armament. The B-25H carried four 50 caliber machine guns in the nose above the cannon. It carried four more in blister packs on the fuselage sides. It carried top turret guns and tail guns. When the B-25H began its run, it could unleash eight 50 caliber machine guns and a 75 mm cannon simultaneously.

This meant that as the pilot lined up his cannon shot, he was also spraying the deck of the enemy ship with 120 rounds of 50 caliber ammunition per second. It turned the enemy ship into a slaughter house before the cannon shell even arrived. Japanese gunners couldn’t stand at their sights. They were cut to pieces or forced to dive for cover.

The B-25H became the most heavily armed aircraft of World War II. But the men who flew it were about to face their greatest test. The Japanese were fortifying their merchant ships. They were adding armor. They were adding more 25mm autoc cannons. The duel between the sky artillery and the Imperial Navy was about to escalate.

By early 1944, the B-25H was arriving in theater. To the uninitiated, it looked like a standard bomber. to the mechanics of the 345th bomb group. It was a maintenance nightmare and an engineering marvel wrapped in olive drab aluminum. The heart of the beast was the T13 E1 cannon. Unlike the M4 field gun used in the earlier G model, this weapon was designed specifically for aircraft.

It was lighter, weighing only 400 lb compared to the M4’s 900. But lighter meant less mass to absorb recoil. The engineers had to create a new recoil system that used a concentric hydro mechanism wrapping around the barrel itself. It was elegant, compact, and brutal. When fired, the barrel recoiled 21 in in roughly 300 milliseconds.

The force transferred to the airframe was calculated at 9,000 lb of thrust. To put that in perspective, the two right cyclone engines pulling the aircraft forward generated only 3,400 lb of thrust. combined. For a split second, the gun was pushing backward three times harder than the engines were pulling forward.

The pilot sitting just feet above the brereech, felt this as a physical blow. Captain Chas Squirt Tipton, a pilot with the 499th Bomb Squadron, described it as having a mule kick the nose of your plane. The deceleration was so sharp that unbutted crew members could be thrown forward. Dust and debris from the floor would float in the air for a second before settling.

But the cannon was only half the equation. The ammunition was the other. The standard round was the M48 high explosive shell. It carried 1.5 lb of T. It was designed to shatter concrete and kill infantry. Against a ship, it would blow a massive hole in the superructure or the hull. But for heavily armored targets, the crews loaded the M61 armor-piercing capped shell.

This round had a hardened steel nose designed to punch through 3 in of face hardened armor plate before exploding. It turned the B-25 into a flying tank destroyer. However, the weapon had a unique quirk that terrified new pilots. The trajectory, the 50 caliber machine guns, fired in a flat, high velocity arc. The 75 mm shell was heavy and slow.

At 3,000 yd, the shell would drop several feet. Pilots had to learn a complex dance of ballistics. They would fire a burst of 50 caliber machine gun fire to walk the tracers onto the target. Once the tracers were hitting the ship’s waterline, they would instinctively lift the nose slightly and fire the cannon.

If they timed it right, the cannon shell would follow the tracers but arc slightly higher, slamming into the exact spot the machine guns were hitting. If they timed it wrong, the shell would pass harmlessly over the ship or splash short. And they had to do this while flying at 280 mph, 50 ft off the water while the ship was shooting back.

The theory was sound, the engineering was proven, but combat is where theory goes to die. On February 15th, 1944, the theory was put to the ultimate test near Cavain, New Ireland. Lieutenant James Jock Henbury was leading a flight of B-25H’s from the 498th Bomb Squadron. His target was a convoy of two Japanese merchant ships escorted by subchasers.

Henibri was 24 years old. He had flown over 50 missions. He was one of the best skip bombers in the Pacific. But today he was carrying the cannon. The weather was typical for the South Pacific, humid with scattered cumulus clouds at 2,000 ft. Visibility was good. Too good. The Japanese lookouts spotted the American planes 5 mi out.

On the bridge of the Japanese freighter, the captain ordered a hard turn to starboard. He knew the drill. Present the smallest target. The ship’s anti-aircraft gunners manning 25mm autoc cannons and 13 mm machine guns swung their weapons around. Henibri didn’t climb to bomb. He dropped. He leveled out at 50 ft.

The ocean surface rushed by in a blur of blue and white. His co-pilot, Lieutenant Don Cotner, called out the range. 3,000 yd. Henry armed the cannon. He armed the four-nose machine guns. He armed the fuselage blister guns 2,500 yd. The Japanese ship opened fire. Tracers whipped past Heniby’s canopy. They looked like angry red hornets.

One round punched through the left wing, leaving a jagged hole. Henibri ignored it. He was locked in a tunnel of concentration. 2,000 yd. Henbury squeezed the trigger for the machine guns. 850 caliber Brownings roared to life. The vibration was intense. The noise was a continuous jackhammer roar. Henibri watched the streams of traces converge on the Japanese ship.

He walked them from the bow to the bridge. He saw pieces of the ship flying off. He saw gunners collapsing. The Japanese fire slackened. They were being suppressed. 1,500 yd. Henebre’s thumb moved to the cannon button on top of the control stick. He lifted the nose a fraction of a degree. Fire. The plane shuddered violently. The cockpit filled with the smell of cordite.

Henibri fought the controls to keep the wings level. A second later, a massive explosion blossomed on the side of the freighter just above the waterline. The 75 mm shell had punched through the steel hull and detonated in the cargo hold. Reloading, shouted the navigator, who was also the canineer from the crawway. 1,000 yd. Henibri kept the machine guns firing.

He could see individual rivets on the ship now. He could see the panic on the deck. Up, screamed the canineer. Henry fired again. The second shell hit the bridge. The entire structure seemed to disintegrate. Glass, steel, and bodies were thrown into the air. 500 yd. Henibri was now committed. He couldn’t turn. He couldn’t pull up.

He had to fly directly over the ship. He held the machine gun trigger down. The Japanese ship was a burning ruin, but there were still men firing rifles and pistols at him. At 300 yd, Henry released his bombs to 500 pounders with 4-second delay fuses. They splashed into the water right next to the hull. He pulled back on the stick.

The B-25 groaned as it pulled up over the ship’s masts, missing the radio antenna by feet. Behind him, the bombs detonated. The hydraulic shock wave crushed the ship’s hull like a tin can. The freighter broke its back and began to settle into the water. The entire engagement from the first shot to the flyover had taken less than 60 seconds.

In 1 minute, a 7,000 ton ship and its cargo were destroyed. Henibre’s plane had fired four cannon shells and over 1,000 rounds of machine gun ammunition. It was brutal. It was efficient and it was terrifyingly personal. When Henry landed back at base, his crew chief counted the holes in his plane. There were 14. One 25 mm shell had passed through the navigator’s compartment, missing the canoner’s head by inches.

Henibri walked around the plane, looked at the cannon muzzle blackened with soot, and reportedly said, “It works, but God helped the guy who has to load it.” While the pilots got the glory and the medals, the men loading the guns paid a different price. Sergeant Frank Papy Ginta was a navigator and caner in the 345th. He was an older man for the unit, hence the nickname.

He described the job of loading the T-13 E1 as wrestling a bear in a phone booth during an earthquake. The B-25 was not a pressurized aircraft. It was noisy, drafty, and smelled of oil and sweat. In the tropics, the temperature inside the fuselage could reach 120°. The canineer had to wear a flack vest, a helmet, and a parachute. He was kneeling in a cramped tunnel next to the nose gear housing.

When the pilot began his run, the plane would start to  and weave. The canineer had to balance on his knees, holding a 15-lb artillery shell. If the plane hit turbulence or took a sudden evasive turn, that shell became a deadly projectile inside the cockpit. There were reports of canineers dropping shells on their own feet, breaking toes.

There were stories of shells jamming in the rack. But the real danger was the breach. The recoil mechanism was violent. If the cantoner’s hand was in the wrong place when the gun fired, the recoiling breach block could crush his fingers or break his arm. There were no safety guards.

There were no sensors to stop the gun if a hand was in the way. It was purely mechanical. And then there was the gas. Despite the ventilators, the cockpit would fill with acrid smoke after a few shots. Eyes would water. Throats would burn. The carbon monoxide levels would spike. Crews would land with splitting headaches and nausea.

Not just from the stress, but from mild poisoning. Sergeant Gintter recalled a mission where the ventilation blower failed. After three shots, he couldn’t see the pilot through the smoke. He was coughing so hard he couldn’t load the fourth shell. He had to crawl back to the navigator’s station and gasp for air from the slipstream vents.

Yet they did it. Mission after mission, they developed a rhythm, a dance, grabb, load, lock, shout, recoil, eject, kick, repeat. They were the unsung heroes of the sky, artillery. They were the men who kept the gunfed while the world tried to kill them. The Japanese were not passive victims. They were skilled, determined, and adaptable warriors.

By mid 1944, Japanese naval commanders had analyzed the American strafer tactics. They realized that the B-25s had to fly straight and level to aim their fixed guns. They realized that the Americans attacked from the beam, which is the side, to present the largest target profile. So, they changed their tactics.

Commander Tamichi Hara, a celebrated destroyer captain and author of the Japanese manual on torpedo warfare, instructed his convoy escorts to change their formation. Instead of sailing in a line, they would sail in a diamond or circular formation. This meant that no matter which direction the Americans attacked from, they would face the broadside firepower of multiple ships.

They also upged their merchant fleet. In 1942, a Japanese freighter might have two machine guns. By 1944, they were bristling with weapons. They mounted 25 millimeter triplebarreled autoc cannons. They mounted captured American 50 calibers. They even mounted depth charge throwers set to explode in the air, creating a wall of shrapnel in the path of the low-flying bombers.

They also learned to use the terrain in the narrow straits of the Philippines and Indonesia. Japanese captains would hug the coastline. They would position their ships so that the American pilots had to fly over jungle covered hills to attack. This gave the pilots only seconds to acquire the target and fire. It nullified the range advantage of the 75 mm cannon. The easy kills were gone.

The turkey shoot was over. Now every attack run was a gauntlet. On May 5th, 1944, a flight of B-25H’s from the 42nd Bomb Group attacked a convoy near Halmahira. The Japanese were ready. Lieutenant Ralph Shorty Wel led the attack. As he lined up on a transport, he saw the entire side of the ship light up with muzzle flashes.

It looked like the 4th of July, Wel later said. Tracers were coming at us like a solid wall. Wel fired his cannon. The shell hit the water short. He fired his machine guns. He saw hits on the deck, but the Japanese fire didn’t stop. A 25 mm shell struck Wensel’s right engine. The engine exploded. The propeller sheared off and flew over the cockpit, missing the canopy by inches.

Wel struggled with the controls. The B-25 yorded violently to the right. He was 50 ft off the water doing 240 mph with one engine burning and a ship full of angry gunners ahead of him. He couldn’t pull up. He couldn’t turn. He did the only thing he could do. He kept coming. He fired the cannon again.

This time the range was point blank. The shell struck the transports bridge. The explosion silenced the forward guns. Wel toggled his bomb release and hauled back on the yolk with both hands. His plane cleared the ship’s mast with zero clearance. The burning engine trailed a plume of black smoke. Behind him, his bombs detonated, blowing the stern off the Japanese ship.

Wel managed to limp his crippled aircraft back to base on one engine. When he landed, the mechanics found over 100 bullet holes in the fuselage. The sky artillery could dish it out, but the question was, how long could they keep taking it? The Japanese were making the cost of doing business incredibly high. And the 75 mm cannon for all its power had a limitation that was becoming fatal. Rate of fire.

In the time it took to fire one cannon shell, a Japanese triplemount 25 mm gun could fire 15 explosive rounds. The math was starting to turn against Papy Guns invention. By the summer of 1944, the war in the Pacific had changed. The desperate defensive battles of 1942 were a distant memory. The United States was on the offensive.

The strategy was island hopping. General Douglas MacArthur and Admiral Chester Nimttz were bypassing major Japanese strongholds, leaving them isolated and starving while seizing key airfields to project power forward. The B-25 Mitchells of the Fifth Air Force were the lynch pin of this strategy. Their mission was simple but brutal, which was to enforce the blockade.

The Japanese garrison at Rabal, once the most terrifying fortress in the South Pacific, was now a prison. 100,000 Japanese troops were trapped there. They had no air support. Their navy had abandoned them. Their only lifeline was the Antron, which was a desperate network of barges and small coastal freighters trying to smuggle rice and ammunition in under the cover of darkness.

The B-25H was the warden of this prison. Commanders like General Kenny understood the grim mathematics of the situation. Every barge sunk meant fewer calories for a Japanese soldier. Every coastal freighter destroyed meant shortages of quinine ammunition and fuel. The strategy was not to storm Rabul, but to suffocate it. For the crews of the Arapaches and the Sunsetters, the war became a daily grind of hunting small targets in dangerous waters.

They weren’t fighting for territory. They were fighting to tighten the noose. But the nature of the targets was changing. The large transports were gone, sunk or withdrawn to safer waters near Japan. The targets were getting smaller. Wooden luggers, motorized sapans, camouflaged barges hidden under mangrove trees. The 75 mm cannon designed to punch through the steel hull of a destroyer was often overkill for a 30-foot wooden barge.

A 15lb high explosive shell would pass clean through a wooden hull without detonating, exploding harmlessly. In the water on the other side, pilots began to complain. They reported through and through hits that failed to sink the target. They had to switch to using the machine guns to soar the barges in half or set them on fire.

The weapon that Papy Gun had fought so hard to build, the weapon that had terrified destroyer captains, was becoming a victim of its own success. It had done its job too well. There were no big targets left to shoot at. While the B-25H was ruling the waves, a new technology was arriving that would ultimately sign its death warrant.

The high velocity aircraft rocket or HVAR developed by the Navy and adopted by the Army Air Forces. The HVAR was 5 in in diameter and carried a 45 lb warhead. It had no recoil. It required no loader. It required no heavy mounting hardware. A B-25 could carry eight of them under the wings. The math was undeniable.

A B-25H with a 75 mm cannon could fire perhaps four rounds in a strafing run. Each round carried 1.5 lb of explosive. Total explosive weight on target was 6 lb. A B-25J carrying eight HVA rockets could fire them all in 2 seconds. Each rocket carried 7.8 lb of explosive. Total explosive weight on target was over 60 lb. And the rockets were safer for the plane.

There was no 9,000lb recoil shock. There was no toxic gas in the cockpit. There was no need for a crew member to wrestle heavy shells in a vibrating tunnel. The pilots loved them. They described the HVAR as having the hitting power of a destroyer’s broadside. They were accurate, deadly, and reliable. General Kenny saw the writing on the wall.

The B-25H with its magnificent complex heavy cannon was a specialist weapon in a war that now demanded versatility. The production lines at North American Aviation switched. The B-25J became the definitive model. It dropped the cannon. Instead, it reverted to Papy Gun’s original concept, which was machine guns. Lots of them.

The solid nose B-25J carried 850 caliber machine guns in the nose alone. With side packs and turret guns, it could bring 14 forward-firing machine guns to bear. When you added eight rockets to the wings, you had an aircraft that could suppress flack, sink ships, destroy pillboxes, and cut down infantry, all without the mechanical complexity of a tank gun.

The era of the sky artillery began to fade. But the cannon didn’t disappear overnight. The crews who had mastered it, the men who had learned the strange dance of the recoil, were stubborn. They knew what the gun could do against a hardened target that a machine gun couldn’t touch. There were still concrete bunkers.

There were still cave entrances. There were still heavy tanks. And for those targets, the cannon had one final act to play. In late 1944, the war moved to the Philippines. The invasion of Leerti and then Luzon brought the fifth air force into direct contact with the main strength of the Japanese army. The targets were no longer ships.

They were bridges, towns, and fortified positions. On December 12th, 1944, the B-25HS of the 345th Bomb Group were tasked with a closeair support mission near Ormac Bay. The Japanese 26th Infantry Division was dug into a series of fortified ridges. They had concrete pill boxes and heavy log bunkers that were impervious to machine gun fire and difficult to hit with bombs.

This was the environment the cannon was made for. Captain Francis Peggy Thompson led the flight. He spotted a Japanese command post situated inside a reinforced concrete building. He couldn’t skip bomb it because the terrain was too rough. He couldn’t strafe it effectively because the walls were too thick. He set up for a cannon run.

He approached at treetop level the propellers chopping through the palm frrons. The Japanese infantry opened fire with small arms. Thompson ignored them. He was hunting the bunker. At 1,000 yards, he fired. The shell smashed into the front wall of the concrete blockhouse. It didn’t just make a hole, it shattered the structure. The delayed fuse detonated the shell inside the confined space. The roof lifted off.

The walls collapsed outward. Thompson fired three more rounds into the Japanese positions on the ridge. Each shot was a precision strike. He was using the airplane as a sniper rifle. It was a demonstration of what the weapon could do in the hands of an expert. It was precise, devastating, and psychologically terrifying to the enemy.

But it was also rare. For every bunker destroyed by a cannon, a hundred were destroyed by napalm rockets and mass bombing. The logistics of war favored volume over precision. The 75 mm ammunition was heavy to ship. The guns required specialized maintenance. The recoil was still cracking airframes. By 1945, most B-25h’s were being stripped of their cannons.

They were replaced with additional machine guns or simply left empty to save weight. The planes were flown until they were worn out, then pushed off the flight decks of carriers or abandoned in aircraft graveyards on remote islands. The experiment was over. The war ended in August 1945. The B-25 Mitchells were scrapped by the thousands.

The aluminum was melted down to make pots, pans, and siding for the housing boom of the 1950s. The story of the Sky Artillery became a footnote. It was seen as a strange detour in aviation history. A moment when engineers got too creative and tried to force a square peg into a round hole. But was it a failure? In the 18 months that the 75mm equipped B-25s operated, they sank dozens of ships.

They destroyed hundreds of barges. They terrified a generation of Japanese sailors. More importantly, they proved a concept that would lie dormant for 20 years until another war in another jungle brought it back to life. In the 1960s, over the skies of Vietnam, the United States Air Force faced a familiar problem.

How do you hit moving trucks on the Ho Chi Min Trail at night? Fast jets were too fast. They needed something that could loiter, aim, and fire heavy ordinance with precision. They built the AC-130 gunship. And what did they put in the side of the AC-130? A 105 mm howitzer. The direct descendant of the concept Papy gun had scribbled on a napkin in Australia.

The idea that a flying artillery battery could dominate the ground was not crazy. It was just ahead of its time. Major Paul Papy Gun survived the war. He was reunited with his family in Manila in 1945. They were malnourished and sick, but they were alive. He had kept his promise. He had fought his way back to them.

Papy Gun died in an airplane crash in 1957. Flying a civilian plane in the Philippines. He died doing what he loved, flying low over the jungle, tinkering with machines, and pushing the limits of what was possible. The B-25H remains a singular machine in history. No other nation attempted to mount a gun of that size on a production medium bomber.

It was an American solution to an American problem which was brute force ingenuity and a refusal to accept that something was impossible. For a brief window in time, the laws of physics were suspended. A bomber became a tank, a pilot became a sniper, and the ocean became a hunting ground for the loudest, hardest hitting aircraft of World War II.

They called it the Mitchell. The Japanese called it a nightmare. The men who flew it just called it the cannon bird.