HMS Graph - Capture

Capture

On 27 August, U-570 spent much of the morning submerged. She had been four days at sea and this was to give respite to a crew that was suffering acutely from seasickness (several had been incapacitated). She surfaced at position 62°15′N 18°35′W / 62.25°N 18.583°W / 62.25; -18.583 at around 10:50 am, and was immediately detected by the radar of a nearby RAF Lockheed Hudson bomber of 269 Squadron operating from Kaldaðarnes, Iceland.

Rahmlow, who had climbed out onto the bridge, heard the approaching Hudson's engines and ordered a crash-dive. However, the aircraft reached the submarine before she was fully submerged and dropped four 250-pound (110 kg) depth charges—one detonated just 10 yards (10 m) from the boat.

The U-boat quickly resurfaced and around ten of the crew emerged. The Hudson opened fire on them with machine guns, but ceased when the U-boat crew displayed a white sheet. An account of what happened was subsequently given to British naval intelligence interrogators by the captured crew members—the depth charge explosions had almost rolled the boat over, knocked out all electrical power, smashed instruments, caused water leaks and contaminated the air on the boat. The inexperienced crew believed the contamination to be chlorine, caused by acid from leaking battery cells mixing with sea-water, and the engine-compartment crew panicked and fled forward to escape the gas. Restoring electrical power—for the underwater electric motors and for lighting—would have been straightforward, yet there was nobody remaining in the engine compartment to do this. The submarine was dead in the water and in darkness. Rahmlow believed the chlorine would make it fatal to stay submerged so he resurfaced. The sea was too rough for the crew to man their anti-aircraft gun so they displayed a white flag to forestall another, probably fatal, depth charge attack from the Hudson—they were unaware the aircraft had dropped all its depth-charges.

Most of the crew remained on the deck of the submarine as the Hudson circled above them. A radio request for help saw it being joined by another Hudson and a Consolidated Catalina flying boat of 209 Squadron, with a full load of depth-charges. The German crew radioed their situation to the German naval high-command, destroyed their radio, smashed their Enigma machine and dumped its parts overboard along with the boat's secret papers. Admiral Dönitz later noted in his war diary that he ordered U-boats in the area to go to U-570's assistance after receiving this report and the U-82 responded, but was prevented from reaching the U-570 by Allied air patrols.

The U-570's transmission was in plain language and it was intercepted by the British. Admiral Percy Noble, commander of Western Approaches Command, immediately ordered a small armada of ships to race to the scene. By early afternoon, fuel levels had forced the Hudsons to return to their base in Iceland. The Catalina, a very long-range aircraft, was ordered to watch the submarine until Allied ships arrived. If none came before sunset, the aircraft was to warn the U-570's crew to take to the water, then sink her. The arrival of the first vessel—the anti-submarine trawler HMT Northern Chief—averted this. The Catalina returned to Iceland after flying in circles over the U-boat for 13 hours.

The German crew remained on board U-570 overnight; they made no attempt to scuttle their boat as Northern Chief had signalled she would open fire and not rescue survivors from the water if they did this. During the night, four more naval trawlers and the destroyers HMS Burwell and HMCS Niagara reached the scene. At daybreak, there was a series of signal lamp messages between the Allies and Germans, with the Germans repeatedly requesting to be taken off as they were unable to stay afloat, and the British refusing to evacuate them until they secured the submarine and stopped it from sinking—the British were concerned that the Germans would deliberately leave behind them a sinking U-boat if they were evacuated. The situation became more confused when a small float-plane (a Northrop N-3PB of 330 (Norwegian) Squadron) appeared. Unaware of the surrender, it attacked the U-570 with small bombs and fired on the Northern Chief (which returned fire). No damage was done and Burwell ordered the aircraft away by radio.

The weather worsened; several attempts to attach a tow-line to the U-boat were unsuccessful. Believing the Germans were being obstructive, Burwell's captain, S.R.J. Woods ordered warning shots to be fired with a machine gun, but five of the German crew were accidentally hit and slightly wounded. With much difficulty, four armed British sailors from the trawler HMS Kingston Agate reached the submarine using a Carley float (a liferaft). After a quick search failed to find the U-boat's Enigma machine, they attached a tow line and carried out the transfer of the five wounded men and the submarine's officers to the Kingson Agate. The remaining crew were taken on board HMCS Niagara, which by this time had come alongside the U-boat.

The ships began slowly sailing to Iceland with the U-570 under tow, and with a relay of Hudsons and Catalinas constantly patrolling overhead. They arriving at dawn on 29 August at Þorlákshöfn. There, the submarine was beached as she had been taking on water and was thought to be in danger of sinking.