The relations between Japan and China suffered in the years after the Second World War and continue to suffer to this day in large part as a result of atrocities committed by the Japanese during their invasion of China and perceived historical insensitivity on the part of the Japanese. The Rape of Nanking, a weeks-long massacre involving horrible violence and the rape of women that took place in 1937, is the most infamous and offensive of these atrocities.

The Meiji Restoration is the name given to the modernization and westernization of Japanese society in the second half of the nineteenth century. As a result of Japan's increasing economic and military power combined with China's subjugation by the British and French, the Japanese came to view the Chinese as a backwards nation that was unable to defend itself.

During the Chinese Civil War, the Nationalist Party, which wanted to install a democratic government in China, was forced off of the Chinese mainland and eventually installed a Chinese state on the island of Taiwan (sometimes called Chinese Taipei). This led to a situation where the majority of Western countries, and Japan, recognized the government of Taiwan as the only legitimate Chinese government until the 1970s. The communist government of mainland China was considered illegitimate by the United States and Japan during the more fractious years of the early Cold War.

Trade between China and Japan, from the end of the Second World War until the early 1970s, was only conducted in an unofficial, black-market form; however, in 1972 (concurrent with Nixon's visit to China), trade relations between Japan and China were normalized and each country is now one of the largest trading partners of the other.

Since the end of the Second World War, the biggest obstacle to friendly relations between the People's Republic of China and Japan has been the memory of Japanese wartime atrocities. In particular, the horrific Rape of Nanking stands out as the most divisive of incidents. This situation is exacerbated by frequent Japanese refusals to recognize and apologize for the atrocities committed during the Second World War. In the twenty-first century, these issues have shown some signs of abating as Japan has issued some formal apologies and offered concessions to the Chinese government. Still, the people of each country remain distrustful of the people of the other country.

The Korean War was fought between the communist government of North Korea and the capitalist government of South Korea. The United States and other democratic and capitalist countries involved themselves on the side of the South Koreans, and China and other communist countries involved themselves on the side of the North Koreans.

The Japanese occupied the Korean peninsula in 1910 in one of their earliest waves of imperial expansion that would mark the next thirty-five years of East Asian history. The Japanese remained in Korea until 1945, when the northern half of the country was liberated by the Soviet Union and a communist government established there and the southern half was liberated by the United States and a capitalist government established there. This would lead directly to the Korean War.

During the Cold War the United States and the Soviet Union never came into direct combat with one another. Instead the capitalist nations of Western Europe and America fought a series of proxy wars against the Communist nations of U.S.S.R. and China. A proxy war is a war fought between two less powerful nations who are each backed by a much more powerful nation. The Korean War is the earliest example of this in the Cold War. It began when North Korea invaded South Korea in 1950. The American government sent troops and resources to the democratic South Korea and succeeded in pushing the North Koreans back into the North, however as the combined forces of America and South Korea marched into North Korea, China became worried that the war might lead to a full scale conflict between capitalism and communism in East Asia and so began to offer support to North Korea. The war eventually ended in an armistice in 1953, but tensions in the region continue to this day.

After World War II, France held Vietnam, which had a communist government led by Ho Chi Min. Most fighting took place in the northern part of the country in a series of guerilla style battles led by small skirmishing forces. These small bands, known as Viet Cong, were victorious against the France and helped create a North Vietnam that was Communist in 1954. By the mid 1960s, conflicts between the two Vietnams warped into open warfare, drawing in the United States openly and the USSR discreetly. The Viet Cong, even when representing a nation state, continued using guerilla tactics to frustrate the American troops.

The Paris Peace Accords of 1973 effectively ended American military involvement in the Vietnam War. It also provided a (temporary) peace between the forces of North and South Vietnam. For their role in the peace treaty, Henry Kissinger and Le Duc Tho were given the Nobel Peace Prize.