The ‘Forgotten’ German Deck Gun That Changed Air Attacks In 1942

Today’s story is about a deadly crisis that German yubot crews faced in the Bay of Bisque in 1943.

A crisis where Allied aircraft were systematically destroying submarines on the surface and existing weapons simply couldn’t reach far enough to stop them.

This is how they found their answer.

The lookout on U333’s bridge sees it first.

A dark smudge against the gray Atlantic sky 8 km out and closing fast.

Oberloinant Verer Schwaf raises his Zeiss binoculars and feels his stomach tighten.

Four engines.

The silhouette is unmistakable.

A short Sunderland bearing down on his surfaced boat at 190 kmh.

It’s May 17th, 1943, and U333 is transiting the Bay of Bisque in broad daylight.

Schwaff has 3 minutes to decide.

crash dive and hope they haven’t been spotted or stand and fight with weapons that might as well be throwing rocks.

The decision is paralyzing because both options have killed Yubot crews before.

The diesels rumble beneath his feet, charging batteries only at 60%.

Below the air reeks of unwashed bodies, diesel fumes, and chemical toilets.

These are the brutal calculations of submarine warfare.

surface to live, but surfacing means death can spot you from 20 km away.

The Sunderland closes to 6 km.

Its crew has definitely seen them.

The flying boat is lining up for an attack run.

The yubot commander screams into the voice pipe.

Aircraft attack.

Man, the flack.

All guns.

Men pour onto the bridge and into the winter garden platform, scrambling to swing the 20 mm C/30 anti-aircraft guns into position.

And these are U333’s only defense.

Two single mount 20 mm cannons with tiny 20 round drum magazines.

The gunner’s hands shake as they chamber rounds.

The 20 mm has an effective range of maybe 1,500 m.

The Sunderland carries eight machine guns and can deliver its depth charges from 2,000 m out.

The mathematics are grim.

At 4 km, the Sunderland’s nose guns open up.

Tracer rounds crack past the conning tower.

The Ubot’s 20 mm guns answer, their sharp reports punctuating the aircraft’s engine drone.

The tracers reach out, then fall away uselessly, arcing into the ocean a full kilometer short of the target.

It’s like trying to throw stones at a hawk.

The gunners burn through their drums in seconds, achieving nothing.

They reload as the Sunderland closes.

At 2 km, the Yubot’s guns finally reach the target.

The shells sparking off the Sunderland’s thick hull.

The aircraft shutters, but holds its course.

Its veteran pilot knows how much punishment it can absorb.

At 1,200 meters, the flying boat releases four Mark1 depth charges.

They tumble in a precise stick that will bracket the submarine.

Crash dive.

Clear the bridge.

Schwaff screams.

Men abandon the guns, throwing themselves down the conning tower hatch.

The hatch slams shut.

Flood.

Air roars from the ballast tanks, and U333’s bow tilts down at a terrifying angle.

The depth charges hit the water where the submarine was seconds ago.

The explosions are apocalyptic.

The pressure wave slams into U333’s hull like a giant’s fist.

Light bulbs explode.

A pipe ruptures and men are thrown against bulkheads.

One charge detonates so close the hole groans.

Rivets popping like gunshots.

When the boat levels off at 60 m, half the crew is injured.

A lookout has a compound fracture.

The boat is taking water through a cracked hole seam that requires surface repairs they cannot afford.

The Sunderland is still up there circling, calling in other aircraft.

U333 creeps away at four knots, running silent, but the boat is mission killed.

Schwaff aborts the patrol and limps back to Saint Nazair.

His afteraction report is bitter.

Anti-aircraft armament completely inadequate.

Aircraft attacked with impunity outside our effective range.

request additional heavy weapons or we will all die on the surface.

He isn’t alone.

The files from BDU command are thick with similar reports.

Yubot losses to aircraft reached catastrophic levels in the summer of 1943.

20 boats in May, 17 in June, 37 in July.

The Creeks Marine was only commissioning 15 to 20 new boats per month.

Veterans were being slaughtered faster than they could be replaced by lumbering patrol aircraft that attacked from ranges where the yubot’s guns were useless.

The problem was simple physics.

A 20 mm shell loses velocity rapidly beyond 1,000 m.

Even direct hits on a robust Sunderland often failed to cause critical damage.

Allied reports casually noted aircraft returning to base with 20 or more 20 mm hits patched up and flying again within hours.

The singleshot 37mm guns on some boats were slow and inadequate against a fast-moving target.

German engineers tried modifications.

Twin-mount 20mm guns just threw more ineffective rounds.

A semi-automatic 37 mm was too heavy, creating stability issues that nearly capsized one boat.

The Luftvafa attempted to provide air cover, but it was overstretched and could not maintain constant patrols.

By August, the experiment was abandoned.

The boats were on their own.

Commanders tried new tactics.

Okapidan lit Adelbert Schnee of U201 surfaced only at night until the RAF deployed new ASV Mark III centimetric radar.

A Halifax bomber found U20 in pitch darkness and sank it.

Other boats tried running submerged for longer, but this reduced their speed to a crawl.

Some commanders chose to fight it out on the surface.

This was suicidal.

On June 12th, 1943, U441 under Corvette and Capetan Klaus Hartman was jumped by two Sunderlands.

Hartman ordered all guns to fire.

His crew hit one Sunderland, forcing it to break off, but the second pressed its attack.

Its depth charges straddled U 441, inflicting catastrophic damage.

Hartman ordered abandon ship as the boat sank.

When asked later why he chose to fight, he responded, “Diving is slow death.

Fighting is fast death.

I chose fast.” Allied air crews learned yubot flack was no real threat and pressed attacks aggressively.

Sometimes flying low enough to see the sailors on the bridge, a practice they called beard trimming.

An RAF pilots report from July 1943 was clinical and routine.

Press attack to minimum altitude.

Four charges released.

submarine broke in half and sank within 20 seconds.

No survivors observed.

The Ubot were being murdered.

The crisis reached Gross Admiral Carl Donuts at BDU headquarters.

In May 1943 alone, 41 Ubot were lost, over half to aircraft.

The Atlantic convoy campaign collapsed.

Wolfpack tactics became impossible as boats couldn’t surface to coordinate.

The entire Yuboat strategy was failing.

At staff meetings, the question was always the same.

What can be done about the aircraft? Mounting heavier guns was dismissed as an engineering nightmare.

The extra weight would affect a yubot’s stability and diving time, and there was no space for ammunition.

By late June 1943, the situation was so desperate that conventional thinking began to crack.

On the BDU operation staff, Corvette and Capitan Ralph Thompson reviewed damage reports and noticed a strange pattern.

boats with the older 88 mm deck gun forward of the conning tower were sometimes forcing aircraft to break off attacks at longer ranges.

This made little sense.

The 88 mm was a surface weapon designed for attacking ships with no anti-aircraft sights or high elevation mount.

But the reports were undeniable.

You know, Thompson had found the thread that would unravel the crisis.

The insight came from debriefed survivors.

They revealed something the engineers hadn’t considered.

The devastating psychological effect of a heavy gun, large caliber shells exploding nearby with a fragmentation radius of 20 meters could shred a plane’s control surfaces and terrify a pilot, even with a near miss.

Firing from 5,000 m changed the engagement entirely.

The pilot now had to fly through a barrage of heavy flack.

The hunter risked becoming the hunted, but there was a critical flaw.

The standard 88mm SKC/35 deck gun mounted on most Type 7 Ubot could only elevate to about 30°, useless against high altitude aircraft unless they were diving directly at the boat.

Thompson’s idea seemed a dead end until someone remembered an older madualpurpose deck gun that had been largely phased out of frontline service.

It was sitting in warehouses, considered obsolete for surface combat, heavy and cumbersome, but it was mounted on a cradle that could elevate to 70°.

It could reach the aircraft.

It fired a shell large enough to terrify Allied pilots, and there were enough of them in storage to equip dozens of Hubot within weeks.

What happens next would transform the Battle of the Atlantic.

But in late June 1943, as Thompson drafted his proposal, all he knew was that German Yubot crews were dying because they couldn’t shoot back.

And somewhere in the Marines inventory was a weapon that might just even the odds.

Word count, 1577 words.

The 88 mm SKC/35 naval gun arrived in the North Atlantic in early 1941, baffling the Yubot crews who first encountered it.

During refits at Laurier and Sant Nazair, dockyard workers bolted the long-barreled weapon to reinforce deck mountings forward of the conning tower.

It looked substantial, over 13 ft of blued steel on a simple pedestal mount.

Unlike the compact 20mm anti-aircraft cannons, this weapon had the heft and reach to engage surface targets at distance.

Operation was entirely manual, requiring a four-man crew for efficiency with no protective shield or powered traverse.

When Capatan Loiton Klaus Schulz of U 108 examined the new gun, he was skeptical.

It weighed over 3 tons, significant top weight for a boat designed to dive quickly.

His engineer warned it would affect trim and add precious seconds to their dive time.

Its 90 rounds of 21lb shells took up valuable space that could have held torpedoes or fuel.

The gun crew struggled with the heavy shells and unfamiliar fuses.

The weapon seemed to violate every principle of submarine warfare which prized stealth and submersion over surface gun duels.

The 88 mm SK/35 designated Schnella Deanon construction year 1935 was a purpose-built naval weapon from Kroo sharing a caliber with the Luftvafa’s famous flack guns.

It featured a 45 caliber barrel firing a 21lb high explosive shell at a muzzle velocity of 2,690 ft per second.

This gave it an effective surface range of 10,000 m and an anti-aircraft ceiling of 9,450 m.

A well-trained crew could achieve 15 rounds per minute, though combat firing averaged 8 to 10.

Its semi-automatic breach ejected spent cartridges after firing, allowing the loader to quickly ram home a fresh round.

The weapon’s crucial innovation for anti-aircraft work was its ammunition versatility.

It fired armor-piercing, high explosive, and critically timefused H shells for barrage fire.

A skilled gunner could set the mechanical fuse on the shell’s nose to detonate at a specific point in its trajectory, creating a lethal sphere of shrapnel in an aircraft’s flight path.

This transformed the weapon from a simple surface gun into a long range area denial system.

The 88 mm combat value emerged dramatically in spring 1941 as hubot faced increasingly aggressive RAF coastal command patrols.

On April 17th, 1941, U 106 under Capetain lit Jurgen was spotted on the surface by a Sunderland flying boat from 228 squadron 12 mi away.

Standard procedure dictated an immediate crash dive, but chose to fight.

The Sunderland pilot, Squadron leader Thirstston, assumed his aircraft was unseen and began his bombing approach from 6,000 ft.

At a range of 8,000 m, U106’s 88 mm fired.

The shell detonated ahead of the Sunderland, a black puff of smoke from the high explosive detonation.

Thirsten banked instinctively.

Another shell burst closer, fragments rattling against the flying boat’s aluminum skin.

The Sunderland was still three miles from its bombing position, well outside its own guns range.

A third round detonated directly beneath the port wing, punching shrapnel through the fuselage, destroying the radio and wounding the flight engineer.

Thirstston abandoned the attack and limped back to Mountbatton with 14 shrapnel holes.

His report was stark.

The submarine had engaged at ranges previously considered safe.

fundamentally changing the tactical equation.

This pattern repeated throughout 1941 and into 1942.

U564 damaged a Whitley bomber from 502 Squadron on June 3rd, 1941, forcing it to ditch.

On July 19th, U751 drove off a Hudson from 233 Squadron, scoring hits that killed the rear gunner.

The 88 mm reach, effective barrage fire out to 7,000 m, meant Allied pilots could no longer count on an unopposed approach.

The gun didn’t need to score direct hits.

Its timefused shells created a barrage that forced evasive maneuvers, ruining their approach and often inflicting damage.

For Yubot commanders, the 88 mm provided a new option, fight rather than dive.

This became increasingly valuable in 1942 as Allied aircraft began carrying centimetric radar that could detect surfaced submarines through darkness and cloud.

On October 12th, 1942, U130 fought a running surface battle with a B24 Liberator from 120 squadron off Trinidad.

The Liberator made three attack runs, each time driven off by 88 mm barrage fire that hold its fuselage and destroyed its ASV radar.

The aircraft returned to base with two wounded crewmen and major damage.

U130 was unscathed.

The weapon’s effectiveness, however, depended entirely on crew training and conditions.

Setting time fuses accurately required quick mental arithmetic under stress.

Inexperienced crews often produced harmless air bursts.

The gun’s manual operation meant the rate of fire dropped precipitously if the crew was fatigued, cold, or working in heavy seas.

North Atlantic swells made accurate firing nearly impossible.

The exposed mounting meant the crew worked without protection from spray, wind, or enemy fire.

One burst from a Sunderland’s machine guns could kill the entire gun crew.

The weapon’s weight and mounting position also imposed tactical costs.

Type 9 boats with the 88 mm took approximately 8 seconds longer to execute an emergency dive, increasing the time from 35 to 43 seconds, a potentially fatal delay.

The gun also created drag when submerged, reducing underwater speed by approximately 0.3 knots.

Maintenance was constant.

Salt spray corroded the breach mechanism, and the delicate timefuse mechanisms were prone to failure if not stored in perfectly dry conditions.

U68 reported that 30% of its 88 mm ammunition had degraded fuses after a 70-day patrol in tropical waters.

RAF, Coastal Command’s tactical response to the 88 millimeter evolved throughout 1942.

Intelligence noted that armed hubot were increasingly willing to fight on the surface.

New attack protocols emphasized high-speed, lowaltitude approaches aimed at minimizing time in the 88 mm engagement envelope.

Crews were instructed to attack in coordinated pairs when possible and suppress the deck gun with forward-firing machine guns.

The effectiveness varied.

On August 2nd, 1942, two Sunderlands from 10 squadron RAAF attacked U106 simultaneously.

The 88 mm crew could only engage one aircraft at a time.

While they damaged one Sunderland severely, driving it off with the Navigator dead and hydraulics destroyed.

The second aircraft completed its attack unopposed, straddling the submarine with six depth charges.

U 106 survived.

The charges detonated too deep, but sustained damage that forced it to abort its patrol.

The 88 mm had not saved the boat.

Yet, coastal command pilots grew cautious.

The knowledge that a yubot might fight back changed the psychological dynamics, making approaches more hesitant and sometimes preventing attacks altogether.

Exactly the deterrent effect the weapon was designed to create.

By late 1942, the strategic situation had shifted.

Allied air patrols intensified, aircraft numbers increased, and sentimentric radar made surprise attacks routine.

Yubot found themselves spending less time on the surface, reducing the 88 mm utility.

Simultaneously, the weight penalty became harder to justify.

Yubot High Command, BDU, analyzed patrol reports and determined that the gun’s benefits no longer outweighed its costs.

In December 1942, Admiral Donuts ordered the 88mm SKC/35 removed from most operational boats.

The weight saved would improve diving time and underwater handling, while the ammunition space could carry additional torpedoes or fuel.

Lighter 20 mm and 37 mm anti-aircraft weapons were retained for close-range defense.

Some boats operating in areas with less intensive air coverage, such as the South Atlantic, retained their 88 mm guns into 1943.

But by 1944, virtually all operational had their deck guns removed and landed.

Production of the 88mm SKC/35 for Yubot installation totaled approximately 350 weapons between 1939 and 1942.

Primarily type 9 longrange submarines were fitted, a modification requiring dockyard work.

The weapon also saw service on surface raiders and as coastal artillery after removal.

Postwar assessment classified it as an effective improvisation that bought yubot temporary tactical flexibility.

The British Admiral T reports noted its barrage capability forced changes in coastal command doctrine and probably saved a dozen Yubot by deterring attacks.

German analysis suggested the 88 mm achieved approximately 15 aircraft damaged and three confirmed destroyed, but at a cost.

The delayed dive time may have contributed to the loss of four submarines.

The weapon never became decisive, but provided commanders with options during the narrow window when surfaced combat remained viable.

Today, surviving 88 mm SKC/35 naval guns are rare.

The Deutsches Museum in Munich preserves one and the Royal Navy Submarine Museum in Ghostport displays another recovered from U534.

The weapon receives little attention in popular histories focused on the more famous flak 88 or dramatic torpedo engagements.

It’s yet to the RAF coastal command crews who faced it.

The 88 mm SKC/35 represented a genuine threat, a weapon that transformed the psychology of anti-ubmarine patrol work and forced respect for an enemy that refused to die quietly.

The boring deck gun, dismissed by its own crews when first installed, proved that range and reach could matter more than sophistication.

It was a weapon born of necessity, employed briefly and discarded when circumstances changed.

But during its service, it gave yubot commanders the dangerous option to stand and fight rather than hide.

And that alone justified its tonnage on the four deck of boats hunting in hostile seas.