Mutually Assured Destruction
Mutually Assured Destruction, or MAD, was a way to avoid war, rather than fight it. Ironically however, it required a large number of weapons.
MAD said that there could be no winner in a nuclear war. This became the strategy on both sides as the main threat moved from bombs to missiles.
It involved holding enough weapons to deter the other side from attacking. NORAD thus drew heavily on this strategy when it came to the defence of North America.