During the final days of World War II, Captain America and his sidekick Bucky attempted to end the murderous rampage of the evil villain Baron Zemo who had attached an explosive device to an experimental drone plane. The two heroes managed to board the plane, but the bomb exploded in mid air, killing Bucky and throwing Captain America into the frigid waters of the North Atlantic where he was frozen in a block of ice until 1964 when The Avengers discovered him and managed to successfully revive him after years of being trapped in a state of suspended animation. Captain America would go on to join The Avengers and become one of the teams most active members.