Plan 15: The Terror of the Time Machine (1986)

President Ronald Reagan orders Regis Stanely to travel back in time to quash the 1917 Bolshevik Revolution in Russia before it begins. Using Dr. Clayburgh's time machine, Stanely encounters a series of "time mishaps," including a visit to Depression-era Chicago, before he ultimately becomes the Omega Man, with the earth decimated by an enormous thermonuclear holocaust.