After decades of standoff on the nuclear arsenals each trained on the other, the world’s two superpowers achieved a real breakthrough 27 years ago with the Intermediate-Range Nuclear Forces (INF) treaty, which was signed by Soviet and American leaders on December 8, 1987.

The thaw in the Cold War that coincided with Ronald Reagan’s presidency and Mikhail Gorbachev’s leadership of the Soviet Union in the 1980s is remembered as a positive turning point in East-West relations. Reagan and Gorbachev seemed to overcome differences based on history, ideology, and geography to become real friends. They held multiple summits devoted to the issue of nuclear weapons, and their exchanges seemed to contain a genuine mutual liking as they traded jokes through interpreters. When Reagan died in 2004, Gorbachev, who won the Nobel Peace Prize for his reforms of the Soviet Union, described him as a rival and friend. But if their shared legacy goes beyond friendly photo ops into achievements of real substance, the INF treaty is a major reason. Reagan and Gorbachev signed the treaty at the White House on this date, and it was approved in Congress the following year.

Before INF, the USA and USSR were more or less playing musical chairs with their respective arsenals. There had been agreements to halt the arms race by freezing the number of nuclear missiles held by each, but both nations were allowed to continue acquiring submarine-launched nukes in exchange for destroying older land-based missiles. INF was the first treaty to actually reduce nuclear arsenals. It targeted intermediate-range missiles (defined as having a range of 300-3,400 miles). By the treaty’s June 1991 deadline, American and Russian arsenals decreased by an estimated 2,692 weapons.

http://www.history.com/images/media/slideshow/ronald-reagan/ronald-reagan-inftreaty.jpg