Which term describes the reduction of tensions between the United States and the Soviet Union during the cold war

The correct answer is Détente

The concept of détente is linked to the new arrangements of the late 1960s and the 1970s. The erosion of the ideological monolithism of the two blocs has given a new connotation to international relations. In addition to adversaries, the USA and the USSR have presented themselves as partners.

Conflicts would no longer focus on direct rivalry between the two powers and would go beyond disputes in Asia, Africa and the Middle East.

Furthermore, it is during this period that negotiations on the limitations of nuclear weapons are established.

i think it was   tsar alexander ii