That Time In WWII An Allied Bomber Captured A German Sub

The HMS Graph U-boat made a lovely addition to the British Royal Navy when they added her in September 1941. She wasn’t always a British vessel, though.

The Graph started life playing for the Germans, in April 1941. By August of that same year, her crew surrendered to the allies after a bomber scared them into submission. It was the only time this happened in history.

The Salad Days For U-570

(German U-Boat |

The term U-boat is an anglicized interpretation of the German U-boot, which is short for unterseeboot. You can do the math on what that means.

The Germans used many unterseeboots in WWI and WWII, so the launch of the U-570 on April 15th, 1941 was not particularly special. As a matter of German SOPs, they took the 570 to the Baltic Sea for torpedo testing.

With everything in working order, the Germans sent this U-boat into service in the Norwegian sea. They had a U-boat base in Lojford, Norway at that point.

These U-boats were best at creating blockades, which is a valuable tactic in war. If you can keep the enemy from moving supplies, you can bleed them two ways: financially and militarily. That was the plan for U-570.

A Green Crew

(German U-boat crews were often inexperienced | source:

It was late August when the German’s discovered a swell of merchant ships passing the south end of Iceland. They sent a total of sixteen U-boats to handle the ships.

This would be U-570’s first war patrol. It would also be her last. The commander of U-570 was Kapitänleutnant Hans-Joachim Rahmlow.

As a U-boat commander, Rahmlow lacked practical experience, only what he received from commanding a training vessel. His second in command also lacked experience. The only one with experience in the leadership team was the engineer, but it would not be enough.

Although inexperienced crews were normative in German U-boats, in the case of U-570, these holes in their collective experience would play into the ultimate outcome of their first engagement.

The Attack


It was still morning on August 27th, 1941. The U-570 spent most of the day submerged. Many of the crew suffered seasickness; some to the extent they could not work. The only action they’d seen so far was a failed attack by a bomber.

When Rahmlow surfaced the U-570, who knows what he was thinking before he saw the plane. Commanding the British bomber flying above them was James Thomson, leader of a British squadron stationed in Iceland.

Rahmlow attempted to escape the bomber, diving fast, but Thomson dropped four depth charges, one of which hit the U-boat hard enough to scare Rahmlow. The hit not only rocked the boat, nearly over, it knocked out their electrical power, killed their instruments, and created water leaks.

Rahmlow feared the hit had discharged chlorine gas, so he ordered the crew to resurface fearing another strike or death from poison gas. Before they exited the vessel, the Germans destroyed everything that had intelligence value, including their Enigma Machine.

Little did Rahmlow know that Thomson had no depth charges left.

Further Complications


War is a messy thing. Once they resurfaced, ten of the German crew exited the vessel. The allies fired upon them at first, but when they saw that the German’s were “waving the white flag,” a piece of white paper, they stopped.

Meanwhile, another bomber joined Thomson in the air. He also radioed for more backup from the Navy. They needed a ship in the water.

Despite the arrival of an allied ship, the crew for the U-570 had to remain on board all night. The allies wanted the Germans to secure the submarine from sinking before the allies would let them off. If they could save the sub, it was worth it. Once it stopped sinking, they could tow it away.

Before they could resolve the situation, a Norwegian float plane, unaware of the situation, appeared then opened fire on the U-boat. The Germans fired back until Thomson was able to radio the Norwegians to stop.

It took three sailors on a life raft from an allied ship to review the U-570, then attach a tow. They remove the crew, then towed the U-boat to Þorlákshöfn beach in Iceland, where British engineers could inspect the vessel.

Once they restored buoyancy in the U-boat, they floated Britain’s newest prize home.

(A wounded U-570 | source:

The irony of the whole story is that there were no chlorine leaks. What Rahmlow smelled was a combination of battery acid and seawater. The actual damage to the U-boat was not that bad.

Not only did the U-570 teach the allies valuable information about the U-boats, she looked great with the British flag.

By October of 1942, she was back in service as the HMS Graph.