The B-25 Strafer That Changed Pacific Airpower “They Said It Would Never Work”

In early 1943, a 50-year-old former Navy pilot was tearing apart brand new B-25 bombers in Australian hangers. His name was Paul Irvin Gun. Everyone called him Papy, and what he was doing was technically unauthorized. The Army Air Forces had spent hundreds of thousands of dollars designing and building these aircraft to drop bombs from medium altitude.

Papy gun was ripping out the bombardier compartment and stuffing forwardfiring 050 caliber machine guns into the nose instead. He was modifying aircraft without authorization. He was violating every specification the aircraft was designed around and he was about to change the entire Pacific Air War. General George Kenny was the commanding general of the fifth air force and commanding general of allied air forces in the southwest Pacific area.

 He looked at this 50-year-old pilot modifying aircraft without authorization and instead of stopping him, Kenny gave him cover because Kenny understood something the procurement bureaucrats back in Washington didn’t. High altitude bombing wasn’t working. The hit rates against Japanese shipping were abysmal. Bombers flying at 13,000 ft gave ships plenty of time to turn away when they saw Bombay doors open.

 Medium alitude bombing was marginally better, but still ineffective. The Japanese were winning the shipping war. And if they kept winning, MacArthur’s entire campaign would stall. Papy gun solution was elegantly brutal. Strip the bombardier position. Install 050 caliber machine guns in the nose and on the fuselage sides.

 Eight forward firing guns in total. Turn the B25 Mitchell from a horizontal bomber into a flying gun platform designed for one purpose only. Strafing ships at mast head height 50 ft off the water. So low the pilots could see sailors jumping overboard before the bombs even hit. The aircraft that resulted was called the Commerce Destroyer.

 It wasn’t designed in Burbank or Englewood. It was designed in Australian hangers by an engineering genius who understood what the fifth air force actually needed. And in March 1943, these commerce destroyers got their first major test. The Battle of the Bismar Sea proved what the Commerce destroyers could do. Pepigun’s modifications had turned the B-25 into a shipkilling machine.

 The strafers bristling with eight forwardfiring 050 caliber machine guns sank an entire Japanese convoy at mast head height. Low-level attack worked. Skip bombing worked. The combination of B-25 strafers and P38 fighter cover had achieved what conventional bombing never could. General Kenny’s pilots had mastered skip bombing, learned to suppress anti-aircraft fire with strafing runs, and developed a doctrine of low-level attack that made them the terror of Japanese shipping throughout the Southwest Pacific.

 The Commerce destroyer concept worked. The aircraft modifications that weren’t supposed to exist just proved they were the only thing that worked. General Kenny didn’t wait to make the approach official. By late 1943, the fifth air force had standardized the commerce destroyer configuration across its B-25 squadrons. The modifications Papygun had pioneered in Australian hangers were now required equipment for any Mitchell operating in the Southwest Pacific.

Low-level attack against shipping became the signature doctrine of Kenny’s command, and the P38 lightnings that made it possible became the essential component of every major strike. But one target remained that seemed to mock everything the fifth air force had accomplished. Rabul Simpson harbor at Rabul was not like the open waters of the Bismar Sea.

 The Japanese had transformed this volcanic caldera on the northeastern tip of New Britain into the most heavily defended naval base in the South Pacific. Ringed by anti-aircraft positions that seem to multiply with every passing month. Intelligence estimates in late 1943 put the number of anti-aircraft guns defending the harbor complex at over 350 with many positioned on the ridgeel lines overlooking the anchorage where they could fire down into any attacking aircraft.

Coming in at 50 ft against a convoy in open water was one thing. Coming in at 50 ft into a bowl surrounded by guns on elevated positions was suicide. The commerce destroyers that had annihilated Japanese convoys were useless against the fortress that sheltered the convoys point of origin. Kenny understood the problem with brutal clarity.

 As commanding general of allied air forces in the southwest Pacific area and commander of the fifth air force, he had built his entire operational approach around low-level attack. High alitude bombing didn’t work. The hit rates were abysmal, and Japanese ships simply turned away when they saw Bombay doors open 13,000 ft above them.

 Medium altitude bombing was marginally better, but still ineffective against maneuvering ships. The low-level tactics that Gun and Kenny had pioneered worked brilliantly in open water, but seemed suicidal against fortified positions. The guns on the hills could track aircraft all the way in and all the way out.

 Pilots who survived their attack run still had to fly back through the same gauntlet they had just penetrated. Losses would be prohibitive. The ships at Rabol could not be ignored. Japanese cruisers and destroyers staging through Simpson Harbor threatened every Allied advance in the theater. MacArthur’s drive toward the Philippines required neutralizing Japanese naval power.

 That naval power was concentrated at Rabal. The conventional bombing campaign had achieved limited results. Some ships damaged, some warehouses destroyed, but nothing that fundamentally degraded Japanese capability to project naval force from the base. Kenny needed a tactical innovation that would allow his commerce destroyers to do what they did best.

 Get in close, attack at mast head height. Get out alive. The question was how to blind those guns long enough to make the attack survivable. And he needed the P38 lightnings to keep the zeros off his bombers’s backs while they did it. The answer came from an unexpected direction. white phosphorus. Fifth Air Force planners had been experimenting with WP bombs throughout 1943, primarily as incendurary weapons against ground targets.

 Phosphorus burned intensely. It ignited anything flammable it touched. It was devastating against personnel. But phosphorus also produced something else. dense white smoke that billowed from impact points in thick clouds that could obscure entire sectors of a battlefield. Someone at Fifth Air Force headquarters, the specific individual is not definitively documented, realized that the smoke producing properties of phosphorus bombs might be exactly what Kenny needed to crack Rabul’s defenses.

The tactical concept was elegantly simple in theory and terrifyingly complex in execution. A first wave of B25s would approach Rabal’s harbor at low altitude, carrying white phosphorus bombs designed to detonate on the hillsides and ridge lines where Japanese anti-aircraft guns were positioned. The phosphorus would serve a dual purpose.

The initial explosions and burning chemical would kill or incapacitate gunners who couldn’t escape the impact zone. The massive smoke clouds generated by the burning phosphorus would blind the surviving gunners to what came next. In the minutes before the smoke cleared, a second wave of commerce destroyers would dive into the harbor to attack the ships anchored there.

 But even blinded anti-aircraft guns weren’t the only threat. Rabol was home to over 100 Japanese fighters. Zeros and other interceptors that would swarm any American formation foolish enough to approach the fortress without fighter escort. This was where the P38 Lightnings became essential. The twin engine fighters of the fifth air force would fly top cover, engaging the Japanese fighters at altitude, while the B-25s slipped beneath them toward the harbor.

 The coordination had to be precise. The P38s needed to arrive early enough to draw the Zeros into combat, but not so early that the Japanese fighters could disengage and dive on the bombers. The B-25s needed to time their phosphorous drops to coincide with maximum fighter engagement overhead. Every element had to click together within minutes or the entire formation would be torn apart.

 The plan required extraordinary courage from every pilot involved. The phosphorus bombing aircraft would be first into the defenses, deliberately targeting the gun positions rather than the ships. They would face the full fury of Rabal’s anti-aircraft network before the smoke could provide any protection. Only if they succeeded, only if enough phosphorus bombs hit enough hillsides to generate enough smoke would the ship killers behind them have any chance of surviving their attack runs into the harbor. Above them all, the P38 pilots

would be outnumbered by Japanese fighters, fighting to keep the sky clear for the bombers below. The Rabbal Air Campaign intensified throughout October and November 1943 as Fifth Air Force prepared for the coordinated assault that would test the phosphorous smoke tactic under combat conditions. Intelligence gathered information on anti-aircraft positions, mapping the overlapping fields of fire that made the harbor approaches so deadly.

 Pilots studied reconnaissance photographs showing the volcanic ridge lines that would need to be shrouded in smoke. The timing would be critical. Phosphorous smoke dissipated relatively quickly, which meant the shipkilling wave had to follow the smoke laying wave within minutes, not the comfortable intervals that normally separated attack formations.

The B25 modifications that Papy Gun had pioneered remained the foundation of the attack force. The Strafers with their eight forwardfiring 050 caliber machine guns would still be the primary ship killers coming in at Mastad height to rake decks with gunfire before releasing skip bombs into hulls at the waterline.

But now those strafers would be preceded by aircraft carrying something new. Phosphorous bombs configured for air burst or contact detonation against the hillside gun positions. The smoke screens that resulted weren’t just incidental byproducts of the phosphorus weapon. They were the primary tactical objective of the first wave.

The P38 Lightning pilots, trained separately, but in coordination with the bomber crews. Their role was fighter suppression, getting to Rabol first, climbing to altitude and drawing the Japanese interceptors into combat before the bombers arrived. The P38’s distinctive twin boom silhouette was already feared by Japanese pilots who called it the forktailed devil for its deadly combination of speed, climb rate, and concentrated nose armorament.

 At Rabal, the Lightnings would need every advantage they possessed. The Japanese had concentrated fighter strength at the base, and the American pilots would be outnumbered in nearly every engagement. Practice missions tested the concept against simulated conditions, though nothing could truly replicate the intensity of what Rabul’s defenders would throw at the attackers.

Pilots who had flown through the relatively lighter defenses of convoy escorts understood that Rabul was a different order of magnitude. The harbor was a killing ground designed specifically to destroy aircraft approaching at low altitude. Every pilot flying the smoke laying mission understood that they would be absorbing the worst of the defensive fire so that their comrades in the shipkilling wave behind them might have a chance.

 The phosphorus tactic wasn’t just tactical innovation. It was a calculated sacrifice of the first wave to enable the second. The fifth air force’s approach represented a fundamental shift in how air power could be applied against heavily defended targets. Highalt alitude bombing had failed to achieve decisive results.

Medium alitude bombing was marginally more accurate but still ineffective against maneuvering ships. The low-level tactics that Gun and Kenny had pioneered worked brilliantly in open water but seemed suicidal against fortified positions. Phosphorous smoke combined with P38 fighter suppression created a third option temporarily neutralizing both the defensive advantage of position and the threat of interceptors so that the proven low-level tactics could be employed even against the most heavily defended targets.

The fifth air force launched its coordinated assault on Rabul. B25s and P38s were tasked with destroying ships anchored in Simpson Harbor. The smoke laying aircraft would fly ahead of the main strike force. Their job was to neutralize the shore anti-aircraft batteries through machine gun strafing and phosphorous bombs.

 The ship attacking squadrons would follow. All B25s would have P38 fighter escort. The P38 Lightnings arrived first. They climbed to altitude over the approaches to Simpson Harbor while Japanese radar operators scrambled to alert their fighter squadrons. Within minutes, Zeros were clawing for altitude to meet them.

The sky above Rabul became a swirling melee of fighters, twin boomed lightnings diving through formations of single engine Japanese interceptors. traces arcing across the tropical sky. Aircraft trailing smoke as they fell toward the jungle below. Below the fighter engagement, the first wave of B-25s approached the harbor complex at low altitude, strafing and dropping phosphorous bombs to suppress the ground anti-aircraft batteries.

 The intent was to saturate the harbor’s defenses in smoke immediately prior to the main strike force attacks. The anti-aircraft fire was murderous. Traces rose from every ridgeel line. Shells burst in black flowers across the bomber’s flight path. Aircraft staggered as shrapnel tore through aluminum skin. Then the phosphorus bombs found their marks.

 The white phosphorus ignited with incandescent fury upon impact with the hillsides and ridge lines. The chemical reaction produced massive clouds of dense white smoke that began to blanket the gun positions. Gunners who survived the initial blasts found themselves choking on phosphorous fumes. Unable to see the harbor below, unable to track the aircraft they knew were coming.

 The carefully cighted positions that made Rabul’s defenses so formidable became blind observation posts. their crews firing into smoke at targets they could no longer see. Through the chemical fog came the commerce destroyers. The B25 Strafers dove toward the harbor at mast head height.

 850 caliber guns per aircraft blazing as they closed on Japanese warships anchored in what they had believed was an impregnable sanctuary. The pilots flew so low they could see the spray kicked up by their own bullets hitting the water. So low they had to pull up sharply to avoid colliding with the ships they were attacking. Skip bombs bounced across the harbor surface and slammed into hulls at the waterline.

Streams of 0.5 caliber fire rad decks and superructures above them. The P38s continued their desperate fight against the Zeros, keeping the Japanese fighters occupied while their bomber comrades completed their attack runs. The smoke from the phosphorus bombs screened the attackers from the surviving anti-aircraft positions just long enough.

 Not perfectly, not completely, but enough to turn what should have been a death trap into a viable attack. Ships exploded. Destroyers and cruisers that had sorted against Allied convoys with impunity found themselves under attack by aircraft they couldn’t effectively defend against. The combination of suppressed anti-aircraft fire, smoke obscured observation, and P38 fighter cover achieved what conventional bombing had failed to accomplish.

Actual destruction of naval assets in their most heavily defended anchorage. The fifth air force lost aircraft. The phosphorous smoke couldn’t blind every gun. Some Japanese fighters broke through the P38 screen, but the loss rate was survivable rather than catastrophic. The tactical gamble had paid off.

 The phosphorous smoke suppression tactic proved itself under the worst possible conditions against the most heavily defended naval base in the South Pacific. But here is where the story takes its strangest turn. The phosphorus tactic worked at Rabal. The commerce destroyers proved they could operate even against heavily defended harbors when properly supported.

General Kenny had cracked the code. His pilots had the tools to destroy any target in the Pacific. And then the strategic situation made all of it irrelevant. Rather than continue paying the price in aircraft and air crew to directly assault Rabul’s defenses, Allied planners chose a different path entirely.

 They decided to bypass the fortress. Surrounding territory was captured. Positions that cut Rabul’s supply lines without requiring a single additional bomb to fall on Simpson Harbor. The Japanese garrison at Rabul was left to wither. No assault, no invasion, no dramatic final battle, just slow strangulation as their supply ships stopped coming and their aircraft ran out of fuel and spare parts.

 The fortress that seemed impregnable was simply ignored into strategic irrelevance. The tactical innovations that made direct attack feasible were never fully employed because strategic wisdom recognized that feasible didn’t mean optimal. General Kenny’s commerce destroyers had proven they could crack any target.

 The phosphorous smoke screens could blind any gun position. The P38 lightnings could hold the sky against any fighter opposition. And then the war moved on without requiring any of it. The garrison at Rabul surrendered when the war ended, not because they had been defeated in battle, because Japan surrendered.

 Those Japanese soldiers spent the last portion of the conflict watching the war pass them by. Their mighty fortress reduced to an irrelevant backwater while the real fighting happened elsewhere. Meanwhile, the man who started it all kept flying. Papy gun flew combat missions despite being older than most pilots in the fifth air force.

 The modifications he’d made in Australian hangers became standard factory production. North American aviation began manufacturing B25 strafers directly from the assembly line with guns gun configurations built in. The man who modified aircraft without authorization became the template for production aircraft. His designs outlived the war itself.

 The most important aircraft designer of the Pacific War never worked for an aircraft company. He worked in Australian hangers driven by engineering genius and determination. The army almost stopped him for modifying aircraft without authorization. Instead, they built his designs into every B-25 that rolled off the production line.

 The B-25 commerce destroyer that Papygun invented became the signature aircraft of the Pacific low-level campaign. Skip bombing, phosphorous attacks, ship hunting sweeps, mast head strafing. All of it depended on the nose guns that a 50-year-old pilot had installed without authorization. The phosphorous smoke screens that cracked Rabul’s defenses were dropped from aircraft he had modified.

 The P38 lightnings that held the sky flew cover for his commerce destroyers. The phosphorous smoke cleared over Rabul within minutes of each attack. The commerce destroyers that flew through it returned to bases across New Guinea to reload and wait for the next mission. The P38 pilots who kept the sky clear, landed with gun cameras full of footage that would be studied for decades.

 The fortress at Rabal still stands. The volcanic caldera that once held the most heavily defended naval base in the South Pacific is now a peaceful harbor. The tactic Kenny’s planners invented changed how air forces thought about suppression forever. The combination of smoke screens, low-level attack, and coordinated fighter cover became standard doctrine.

 The fifth air force proved that even impossible targets could be cracked with the right innovation. And the commerce destroyers that Papy Gun built proved that sometimes the best weapon is designed by someone willing to challenge how things had always been