Synopsis for
WarGames (1983)

David Lightman (Matthew Broderick) is an intelligent, underachieving teen who spends most of his free time playing arcade video games or messing around on his computer. During an automated modem search, he finds a strange computer that appears to be affiliated with a game company. A list of games appears, but Lightman doesn't have the password. After doing extensive research, he correctly guesses it. As would-be girlfriend Jennifer (Ally Sheedy) watches, he begins playing "Global Thermonuclear War" and targets his hometown (Seattle) and Las Vegas for Soviet strikes.

Unknown to the teens, the computer behind "Global Thermonuclear War" is not a game software company -- it is the War Operations Plan Response (W.O.P.R.) -- a top-secret military system that helps the Air Force decide what to do in the event of a Soviet attack. On their situation screens deep below Cheyenne Mountain, Colorado, the military actually thinks a first-strike is occurring. Top programmer Dr. McKittrick (Dabney Coleman) figures out what has happened, but it seemed all too real for a few minutes.

The government soon finds out who broke into their system, and Lightman is arrested and taken to Cheyenne Mountain for debriefing. It is assumed that he is affiliated with the Soviet KGB! He realizes that the W.O.P.R. is still "playing" Global Thermonuclear War, and needs to be stopped. The computer is feeding false data to the Americans, trying to get them to "move." General Beringer (Jack Corbin), a hawkish sort, is putting US forces on increasingly higher levels of Alert (known as Defense Conditions, or DefCon). When the computer convinces him that full-scale Russian attack is inbound, the General will order a counterattack.

Lightman cleverly escapes from Cheyenne Mountain, seeking Dr. Stephen Falken (John Wood), the original programmer of W.O.P.R. Dr. Falken grew increasingly concerned about the program, took an assumed name and retired to Oregon. Jennifer helps Lightman to find the Doctor, and they manage to convince the cynical programmer to stop World War Three.

At the last minute, while W.O.P.R. is busy feeding "game" data of inbound Soviet nuclear missiles to General Beringer's staff, Lightman and Falken arrive. They convince the General to wait and see if actual nuclear hits take place (which of course doesn't happen). The computer then tries to "guess" the encrypted launch code that will allow it to launch the US missiles and "win." Lightman and Falken try playing Tic-Tac-Toe against the super-computer, which ultimately teaches it the concept of futility. Just before launching the US missiles, W.O.P.R. quickly runs all the possible nuclear scenarios looking for a situation where it can truly triumph. It ultimately decides that Global Thermonuclear War is futile: there is no winner. Better to play a nice game of Chess.