On 9th May 1941 a Type IXC U-Boat - U-110, Commanded by KapitanLeutnant Fritz-Julius Lemp was attacking Convoy OB318 in the North Atlantic, South of Iceland along with U-201. Lemp had already sunk 2 ships but whilst viewing the sinking of the 2nd ship he left his periscope up just a moment too long and the British Corvette HMS Aubretia raced in for the attack and dropped depth charges. U-110 was badly damaged and almost helpless. 2 destroyers then joined the hunt - HMS Bulldog & HMS Broadway and a 2nd depth charge attack forced the U-110 to surface. Lemp ordered "Abandon Ship" and as the crew began to evacuate they came under gunfire from the 3 Royal Navy ships, the crews believing that the U-Boat's Deck Gun was about to be used against them. Realising that the crew were abandoning the U-Boat they ceased fire. HMS Bulldog then set course to Ram U-110 but at the last minute her Captain - Joe Baker Cresswell hove to and strafed the Submarine. Realising that there might be a chance for a capture, Baker Cresswell sent a boarding party to salvage as much equipment as possible. Lemp meanwhile had realised that U-110 was not sinking and ordered a crewmember back to open the seavalves. He got there but only salvaged a few personal items, ignoring the secret material left inside. Bulldog's boarding party arrived and stripped U-110 of anything portable, including her Enigma Cypher Machine and all the Code Books. U-110 was then taken under tow by HMS Bulldog but sank before reaching Scapa Flow in the Orkney Islands, North of Scotland. U-110's crew knew nothing of the items salvaged from their Submarine and went into captivity none the wiser. The material taken from U-110 was sent to Bletchley Park where the Code Breakers had a field day. This was the break they had waited for as the Kriegsmarine's Enigma Messages had been particularly hard to break in to. Now they had an insight in to the Naval Enigma and gradually the information that was being gleaned was used to route Convoys away from the hunting U-Boats. For almost a year the amount of Allied ships being sunk dramatically fell. GrossAdmiral Karl Donitz suspected that something was amiss but was unable to find any definite evidence that there was a serious breach of security. In 1942 a 4th rotor was added to the U-Boat Enigma Machine and this stopped the Allied Code Breaking effort in it's tracks. All of a sudden the information tap was turned off and the Allies found themselves in the dark once again. Now there were more U-Boats in the Atlantic hunting in "Wolfpacks" and sinkings were increasing alarmingly. It would take almost another year before the Allies broke in to the new "Shark" Enigma Messages being sent between Donitz's Headquarters in L'Orient and his U-Boats at sea. This is the incident that the Film "U-571" is loosely based on.