were preceded by the shorter Type VIIB submarines. U-664 had a displacement of when at the surface and while submerged. She had a total length of, a pressure hull length of, a beam of, a height of, and a draught of. The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of for use while surfaced, two Siemens-Schuckert GU 343/38–8 double-acting electric motors producing a total of for use while submerged. She had two shafts and two propellers. The boat was capable of operating at depths of up to. The submarine had a maximum surface speed of and a maximum submerged speed of. When submerged, the boat could operate for at ; when surfaced, she could travel at. U-664 was fitted with five torpedo tubes, fourteen torpedoes, one SK C/35 naval gun, 220 rounds, and a C/30 anti-aircraft gun. The boat had a complement of between forty-four and sixty.
Service history
The boat's career began with training at 8th U-boat Flotilla on 17 June 1942, followed by active service on 1 November 1942 as part of the 9th Flotilla for the remainder of her service. In five patrols she sank three merchant ships, for a total of.
First Patrol
On her first day of active service she was attacked by a US Catalina. The depth charge attack was so effective that she had to return to base in France.
Convoy ONS 167
Outward bound from Biscay on her second patrol, U-664 made a chance sighting of the slow convoy and radioed its position to base. Karl Dönitz ordered Graef to shadow the convoy while other boats were rounded up to form Wolfpack Sturmbock. However the boats were well scattered and failed to make contact with the convoy, so on the night of 21 February 1943, Graef became impatient with waiting and decided to attack alone. With one spread of torpedoes, Graef sank the American steamer Rosario and the Panamanian tanker H H Rogers.
On 8 August 1943 U-664 fired three torpedoes at the escort carrier in a surprise attack, before USS Card was able to respond and forced her to dive. The following day, on 9 August 1943, USS Card got her revenge. U-664 was sunk in the North Atlantic in position, by depth charges from USN Grumman Avenger aircraft launched from the carrier. Seven crew members were killed or drowned; 44 others were rescued by USS Borie after seven hours in the water.
