Opening credits prologue: In 1942, Russia had been invaded to a depth of a thousand miles, and her armies seemed crushed. The world didn't know that these same "beaten" armies would turn, take back every foot of ground they had lost and then invade Germany itself.
One night in this same year, 1942 . . . .under cover of fog . . . .Russian engineers were engaged in a strange activity . . . .on a river, facing the German lines . . . . .