|Ordered||15 Aug 1940|
|Laid down||11 Oct 1941||Howaldtswerke Hamburg AG, Hamburg (werk 817)|
|Launched||5 Oct 1942|
|Commissioned||16 Nov 1942||Oblt. Wolfgang von Eickstedt|
|Successes||No ships sunk or damaged|
Surrendered at Narvik, Norway on 9 May 1945.
Transferred to Loch Eriboll, Scotland, on 19 May and later to Lisahally for Operation Deadlight.
Operation Deadlight (post-war Allied operation, info)
The U-boats that were in the Narvik area at the end of the war were all moved to the Skjomenfjord upon Allied orders to avoid conflicts with the Norwegians on 12 May. On 15 May, a German convoy of five ships (the fleet tender Grille with the staff of FdU Norwegen aboard, the fleet oiler Kärnten, the repair ship Kamerun and the depot ships Huascaran and Stella Polaris) and 15 U-boats (U-278, U-294, U-295, U-312, U-313, U-318, U-363, U-427, U-481, U-668, U-716, U-968, U-992, U-997 and U-1165) left for transfer to Trondheim, but was intercepted after two days by the 9th Escort Group off the Norwegian coast and officially capitulated. While the ships were allowed to proceed to Trondheim, the U-boats were escorted to Loch Eriboll, Scotland, arriving on 19 May. All U-boats were later that month transferred to Lisahally or Loch Ryan for Operation Deadlight.
U-668 operated with the following Wolfpacks during its career:
Grimm (31 May 1944 - 6 Jun 1944)
Trutz (17 Aug 1944 - 26 Aug 1944)
Schwefel (22 Sep 1944 - 25 Sep 1944)
Zorn (26 Sep 1944 - 1 Oct 1944)
Grimm (1 Oct 1944 - 2 Oct 1944)
Panther (16 Oct 1944 - 10 Nov 1944)
Stier (25 Nov 1944 - 18 Dec 1944)
Hagen (17 Mar 1945 - 21 Mar 1945)
Attacks on this boat
16 May 1944
17.15 hrs, WNW of ┼lesund, Norway: Norwegian-crewed Sunderland JM667 (RAF Sqdn 330/V, pilot S/Lt C.T. Johnsen) attacked as U-668 was transiting between Bergen and Skjomenfjord. U-668 met the initial approach with heavy AA fire and evaded the single depth charge dropped. Four depth charges dropped on the port side during the second run caused minor damage, and one crewman suffered a bullet wound. The Sunderland was hit by flak in the fuselage and starboard wing, damaging both starboard engines, and a shell which exploded in the cockpit killed the nose gunner and wounded two more crew. The Sunderland barely made it back to Sullom Voe on three engines. (Sources: Franks/Zimmerman, Axel NiestlÚ)
1 recorded attack on this boat.
Men lost from U-boats
Unlike many other U-boats, which during their service lost men due to accidents and various other causes, U-668 did not suffer any casualties (we know of) until the time of her loss.