In the closing days of World War II in 1945, Bucky’s fate took a dark turn when he seemingly perished in a plane explosion while on a mission with Captain America. Both are assumed dead by the U.S. military. However, Rogers is frozen alive by the freezing waters of the North Atlantic, the super-soldier serum in his system keeping him alive and in suspended animation.
Bucky, on the other hand, is found in the water by USSR General Vasily Karpov and the crew of a Russian patrol submarine. Barely alive, his body partially preserved by the freezing waters, and is able to be revived. Along with the loss of his left arm, he has brain damage and amnesia as a result of the explosion and his time in the water. Realizing he still has his learned combat skills, expertise, and combat instincts, Karpov sends him to the secret Soviet agency Department X.