The nap that led the U.S. into World War I

Heinrich Albert was a German diplomat and accused spy. While riding the subway in July 1915, he fell asleep before being startled by a sudden stop and exiting the train abruptly. He accidentally left his briefcase filled with classified files, which fell into the hands of the Secret Service agent tailing him. The US government leaked these files to the press, increasing American public opinion further toward the war.