I think the above answers cover much of this idea, with a few important nuances and details left out.
The nuclear arms race did include ever advancing, and ever more competitive technologies. From simple atomic bombs dropped from airplanes, each side quickly progressed to Hydrogen bombs, then to ballistic missiles, then to multiple warheads, then to missiles that were submarine based. As long as the competition continued, the technology advanced.
Also, the arms race was incredibly expensive, involving literally hundreds of billions of dollars. In 1960 alone, for example, while our missile fleet was being developed, 60% of all spending for the US budget was for the military. Just maintaining the nuclear arsenal we currently have costs several billion per year. The MX missile program under Reagan cost $20 billion to develop. So this is money in both countries that could not be used for more constructive, positive social good.
To me, the main features of the nuclear arms race were these:
- The race to develop delivery systems. At the start of the arms race, nuclear weapons were meant to be delivered by long-range bomber aircraft. The two sides raced to develop missiles that could deliver the weapons farther and faster.
- The race to develop more destructive weapons -- this started with the development of thermonuclear weapons.
- The race to have so many weapons as to be able to survive a first strike and fight back. Both sides wanted to be able to destroy the other even if they were surprised by a nuclear attack.
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.
The nuclear arms race was a competition for supremacy in nuclear warfare between the United States, the Soviet Union, and their respective allies during the Cold War. During the Cold War, in addition to the American and Soviet nuclear stockpiles, other countries also developed nuclear weapons, though none engaged in warhead production on nearly the same scale as the two superpowers.