DEFCON 1 takes place during the cold war from 1950 to 1990. All cards and technologies are historically based.

Featuring different gameplay for each number of players:
2 players - Frontal Shock Game, nervous and tense.
3 players - Death Circle Game with secret objectives.
4 players - Semi Cooperation Game and Secret Objectives Game.
5 players - Secret Objective Game.

Each of the 5 aymmetrical blocs has its own strengths and weaknesses, through its own Technological tree, Mission and Objective cards, and even scalable pool of Units. Each player has Mission cards in their hands, and will gain rewards upon fulfilling each of them, bringing them closer to victory. As the DEFCON level decreases, depending on the actions of the players, new strategical options will become available like building nuclear bombs. There is also a Space Race which allows you to earn Influence and to add new Spatial Technologies on your Technological tree.

The game is played in 5 phases:
[0] Initialization: Refill your hand and collect resources (Oil, Uranium, Influence, R&D) depending on the zones under your control.
[1] R&D: With Research you may unlock Technologies. You may also invest in the Spatial Race.
[2] Political: With Influence, you have a possibility to Destabilise zones or take the Political control of the Destabilised zones.
[3] Production: Then, you may Produce available Units in zones you control that contain a Factory. You may also upgrade units.
[4] Atomic: If the DEFCON level has reached level 1, you may launch nuclear bombs (i.e. if you own the Technology).
[5] Warfare: Finally you may Redeploy units, Launch Attacks on Sea, Bombard, then Redeploy units, Launch Attacks on Land.