China. The Khmer Rouge had taken control of Cambodia in 1975 and became one of the most brutal regimes in world history. The newly unified Vietnam and the Khmer regime had poor relations from the outset as the Khmer Rouge began massacring ethnic Vietnamese in Cambodia, and then launched raiding parties into Vietnam. The Khmer Rouge allied itself with China, but this was not enough to prevent the Vietnamese from invading them and destroying the regime in 1979. While unable to save their Cambodian allies, the Chinese did respond to the Vietnamese by invading the north of Vietnam on a punitive expedition later in that year. After a few months of heavy fighting and casualties on both sides, the Chinese announced the operation was complete and withdrew, ending the fighting. The United States played only a minor role in these events, unwilling to get involved in the region after its debacle in Vietnam. The extremely visible disintegration of the communist bloc played an important role in the easing of Sino-American tensions and in the progress towards East-West Détente. Détente and changing alliance In the course of the 1960s and 1970s, Cold War participants struggled to adjust to a new, more complicated pattern of international relations in which the world was no longer divided into two clearly opposed blocs. The Soviet Union achieved rough nuclear parity with the United States. From the beginning of the post-war period, Western Europe and Japan rapidly recovered from the destruction of World War II and sustained strong economic growth through the 1950s and 1960s, with per capita GDPs approaching those of the United States, while Eastern Bloc economies stagnated. China, Japan, and Western Europe; the increasing nationalism of the Third World, and the growing disunity within the communist alliance all augured a new multipolar international structure. Moreover, the 1973 world oil shock created a dramatic shift in the economic fortunes of the superpowers. The rapid increase in the price of oil devastated the U.S. economy leading to "stagflation" and slow growth. Détente had both strategic and economic benefits for both sides of the Cold War, buoyed by their common interest in trying to check the further spread and proliferation of nuclear weapons. President Richard Nixon and Soviet leader Leonid Brezhnev signed the SALT I treaty to limit the development of strategic weapons. Arms control enabled both superpowers to slow the spiraling increases in their bloated