Mutually assured destruction (MAD) was a military doctrine during the Cold War where the United States and Soviet Union deterred the use of nuclear weapons based on the idea that a nuclear attack by one side would be met with an overwhelming nuclear response by the other, resulting in both sides' destruction. The doctrine was based on both sides having enough nuclear weapons to destroy the other and neither side using them first due to the retaliation and assured destruction that would follow. This tense nuclear standoff helped prevent direct military conflict between the two superpowers.