On 23 April 1945, while towing targets for U.S. Navy bomber exercises off the coast of Maine, Eagle 56 was sunk by the German submarine U-853.

[1] Eagle 56 was one of 60 Eagle-class patrol craft built by Henry Ford late in World War I as submarine chasers, none of which saw action.

[3] Eagle 56 remained almost constantly at sea during the Second Happy Time[3] of the Battle of the Atlantic, during which Axis submarines attacked merchant shipping along the east coast of North America.

[3] At noon on 23 April 1945, Eagle 56 exploded amidships, and broke into two pieces[2] 3 mi (4.8 km) off Cape Elizabeth, Maine.

[3] Selfridge obtained a sharp, well-defined sonar contact during the rescue and dropped nine Mark IX Mod 2 depth charges without obvious result.

On 1 June 1945, Rear Admiral Felix X. Gygax wrote, "at least equal evidence to support the conclusion that the explosion was that of a device outside the ship, the exact nature of which is undetermined.

[5] Because the Allies had cracked Germany's codes, United States intelligence knew in 1945 that U-boats had been sent across the North Atlantic to disrupt shipping in hopes of obtaining better surrender terms.