On the nuclear weapons front, the United States and the Soviet Union pursued nuclear rearmament and developed long-range weapons with which they could strike the territory of the other.In August 1957, the Soviets successfully launched the world's first intercontinental ballistic missile (ICBM), and in October they launched the first Earth satellite, Sputnik 1. The launch of Sputnik inaugurated the Space Race. This led to the Apollo Moon landings by the United States, which astronaut Frank Borman later described as "just a battle in the Cold War." A major Cold War element of the Space Race was satellite reconnaissance, as well as signals intelligence to gauge which aspects of the space programs had military capabilities. Later, however, the US and USSR pursued some cooperation in space as part of détente, such as Apollo–Soyuz.