The Armament race
The United States held the secrets and technology to create the atomic bomb alone at first, making her the most powerful in the world. The US wished to stay in first place, ahead of the Soviet Union as the Cold War developed, . Meanwhile, Stalin was determined to make his country in to a great power with nuclear capability to compete with America.
The post-war arms race began, and both sides started spending huge sums of money to develop effective ways of targeting each other. Although they knew a missile attack on the other country would in turn destroy their own country as well, they justified the building up of arms as a way of deterring the enemy.