Chinese foreign policy has undergone several paradigm shifts over the course of the 20th century. The country was plagued by foreign interference early in the 20th century and then subjected to a brutal occupation by Imperial Japan prior to the outbreak of and during World War II. The fall of Japan led to internal strife where Chinese communists came to dominate the country and conquer its outlying areas and neighbors, primarily Tibet. The communist orientation of the government led to a substantial level of support for the Soviet-backed northern half of Korea and both covert and overt support for North Korea during the Korean War. During this period, considered the start of the Cold War, Chinese and Soviet foreign policy objectives aligned, but the relationship soon cooled. China fell out with the Soviet Union and oriented itself around a policy where it was set apart from the United States and the Soviet Union. Before the Soviets, China sought rapproachement with the United States.
Since the advent of communism in China, the country's main priority has been to seek and gain official diplomatic recognition for its government. The communist takeover of the mainland forced hundreds of thousands of nationalists off the mainland, finding Taiwan as a refuge. The island split from the mainland, forming its own country, and earned recognition as the legitimate government of mainland China from many Western powers. For decades, Taiwan would supposedly represent China internationally, though clearly as a rival to the communist government on the mainland. Urged on by the United States, Western states adopted a non-recognition policy toward the communist government.
Internationally isolated, the People's Republic of China (PRC) focused on relations with the Soviet Union, North Korea and Eastern Bloc countries. With the Soviet boycott of the United Nations, China found itself at war with the United Nations in Korea as the North's primary backer. But that war and its significance representing common ground with the Soviet Union would become more significant as a point where China exerted its own influence without subjugation to or in conjunction with the Soviets.
China entered into the Non-Aligned Movement during the Cold War and pursued relationships with third-world nations that might otherwise become strong allies with the Soviets. By the end of the 1950s, the PRC and the Soviet Union were amidst a strong fallout. By the end of the 1960s, political disagreements over the use of force, differences over either's military actions and border clashes were coming to define the relationship. The Vietnamese occupation of Cambodia, later Soviet occupation of Afghanistan and the Chinese war with India were tremendous obstacles that were never fully overcome between the two communist giants.
Given its relationship with the Soviet Union and its pursuit of international legitimacy, the PRC pursued a closer relationship with the West. Through some unique diplomacy, the United States and China recriprocated representatives and patched up their rivalry. The two countries established formal ties by 1978 and have since expanded economic cooperation. However, the clashes with Vietnam in 1979 over their maritime border have preceded a long rivalry that now sours relations with the United States, which has sought rapproachement with the government of Vietnam. Since the end of the Cold War, primarily the Tiananmen Square clashes in 1989, political differences between the United States and China have been pronounced. The United States continues to agitate China about its human rights policies, and they repeatedly clash in international forums over economic sanctions against rogue regimes and military actions. In early 2001, an American navy intelligence plane near the coast of China made an emergency landing after a mid-air collision with a Chinese interceptor fighter plane, resulting in a weeks-long diplomatic crisis between the two countries.
China has used its economic ascendency and prominent position in the United Nations effectively since the end of the Cold War. Since the collapse of the Soviet Union, China has sought improved ties with Russia. This has included resolving border disputes between the two countries. Additionally, it has expanded its economic and political reach by exploiting the end of the Soviet-Indian relationship to mend relations, as well as coming to group agreements with Central Asian countries formerly under the control of the Soviet Union. It has also participated in several multilateral Asian meetings and agreements, namely with the greater economic powers Japan, India, Australia, New Zealand and South Korea. However, the PRC has been protective of its power and remained opposed to India or Japan joining the United Nations Security Council following any reforms. Additionally, several border disputes with China's smaller neighbors have impeded the country's ability to expand its own influence against that of the United States.
China has pursued a more open economic policy, including joining several international organizations. China joined the World Trade Organization after several years of isolation. The country also holds much of the debt owed by Western countries, most notably of the United States. American politicians and analysts have accused the Chinese of undervaluing their currency in order to maintain robust international investment, though China disputes this.