Détente was a period of reduced hostility and improved relations between the United States and the Soviet Union during the Cold War, from the late 1960s to 1979. The term "détente" comes from the French word for "relaxation" and refers to the relaxation of strained relations, especially political ones, through verbal communication. The period of détente saw better communications and a greater level of respect between the nuclear superpowers. It began in the mid-1960s and continued into the 1970s, and was characterized by warm personal relationships. Détente led to formal agreements on arms control and the security of Europe, including the signing of the Nuclear Nonproliferation Treaty in 1968 and the Strategic Arms Limitations Talks in 1972. However, the breakdown of détente in the late 1970s stalled progress on arms control, and ultimately the United States and the Soviet Union had different visions of what détente meant and what its pursuit would entail. Détente ended after the Soviet invasion of Afghanistan in 1979.