What were the main features of the nuclear arms race?

The term 'Nuclear Arms Race' refers to the race for supremacy between the two super powers the U.S.A and the U.S.S.R. to manufacture and stockpile nuclear arms. The race was both quantitative, that is, who will possess more weapons and qualitative, that is, whose weapons will be more lethal and destructive.

In the initial stages the U.S.A., especially after the bombing of Hiroshima and Nagasaki, dominated the race. They unlike the Soviets possessed delivery systems which could bomb targets in faraway Russia with ease.

However, this changed when the Soviets successfully tested the ICBM in 1957  resulting in the "Missile Crisis" in America.

In the next phase America gained an exponential advantage with the introduction of the MIRV capability in their ICBMS. With this technology The ICBMS of the U.S.A. could destroy multiple Soviet targets simultaneously. The Russians however mastered this technique by 1974.

In the 80's with the introduction of Regan's 'Star Wars' program the nuclear arms race entered the space era.

By the 90's with the collapse of the Soviet Union the nuclear arms race had ended and on 24th September 1996 the U.S.A. and other nuclear weapons states along with 60 other non-nuclear states signed the CTBT thus formally ending the nuclear arms race.