Pax Atomica is one of the terms used to describe the period of severe tensions without a major military conflict between the United States of America and the Soviet Union during the Cold War. The phrase refers to the argument that the stability between the two superpowers was caused by each side's large nuclear arsenals which led to a state of Mutually Assured Destruction (MAD). That is, if one of the superpowers would have launched a nuclear attack, the other would have responded in the same way. This threatened the complete destruction of both countries and probably the entire northern hemisphere. John Lewis Gaddis has described the period as the Long Peace.