The Cold War between the United States and Soviet Union saw both sides attempting to maintain or expand their sphere of influence while avoiding all-out war. A key factor was the concept of deterrence. By demonstrating its technological superiority, each side hoped to persuade the other that a war would be unwinnable. The resulting arms race was a major source of tension throughout the Cold War, as was the closely linked space race.

The Start of the Arms Race

The defining weapon of the Cold War was the hydrogen bomb, or H-bomb, which was a thousand times more destructive than the atom bombs used in the final days of World War II. The first experimental H-bombs were exploded by the United States in 1952 and by the Soviet Union in 1953. Although H-bombs were never used in warfare, a succession of increasingly powerful test explosions contributed to the rising tension between the two countries. The largest H-bomb of all, the Tsar Bomb, was detonated by the Soviets in 1961.

The Bomber Gap and the Missile Gap

Of equal importance to the H-bomb was the ability to deliver the bomb to the enemy. The arms race encompassed long-range bombers and ballistic missiles as well as their H-bomb payloads. The aim was to stay ahead of the enemy, but in order to do this it was necessary to know just what the enemy's capability was. The uncertainty over Soviet weapon numbers led to tensions in the United States from the mid-1950s through the mid-1960s, with many observers perceiving first a "bomber gap" and then a "missile gap" relative to the Soviet Union’s capabilities.

The Strategic Importance of Space

An orbiting satellite is one of the most effective ways to spy on an enemy's military capabilities. This was one of the original motivations for the space race. Another was the fact that a space launcher uses the same basic technology as an intercontinental ballistic missile. Putting a satellite into orbit proved that a country could launch a missile against an enemy thousands of miles away. The race into space was won by the Soviets, who launched Sputnik 1 in October 1957 using a modified ballistic missile. The United States followed with Explorer 1 in January 1958.

The Race to the Moon

The space race evolved into a tensely fought battle for technological supremacy between America and the Soviet Union. The objective of putting a man on the Moon became a symbolic goal. Although the Soviets led the space race in its early years, the United States gradually pulled ahead. When Apollo 11 landed on the Moon in July 1969 it was an American, Neil Armstrong, who first set foot on its surface. Another Apollo astronaut, Frank Borman, put this in its historical context by saying, "Because, after all, the Apollo program was just a battle in the cold war."