After which Cold War event did the United States and the Soviet Union enter a nuclear arms race? A. Mao Zedong’s newly founded People’s Republic of China formed an alliance with the Soviet Union.

B. Korea was divided at the 38th parallel into two parts.

C. Communist leader Kim Il Sung prepared the North Korean army.

D. The Soviets detonated their first atomic bomb in 1949.

E. John Dulles, US secretary of state, introduced the policy of brinkmanship.