Korea's traditional religions are Buddhism and Shamanism. Christian missionaries arrived as early as the 16th century, but it was not until the 19th century that major missionary activity began. Pyongyang was a center of missionary activity, and there was a relatively large Christian population in the north before 1945. Although religious groups exist in North Korea today, the government severely restricts religious activity.

By the first century AD, the Korean Peninsula was divided into the kingdoms of Shilla, Koguryo, and Paekche. In 668 AD, the Shilla kingdom unified the peninsula. The Koryo dynasty--from which Portuguese missionaries in the 16th century derived the Western name "Korea"--succeeded the Shilla kingdom in 935. The Choson dynasty, ruled by members of the Yi clan, supplanted Koryo in 1392 and lasted until Japan annexed Korea in 1910.

Throughout its history, Korea has been invaded, influenced, and fought over by its larger neighbors. Korea was under Mongolian occupation from 1231 until the early 14th century. The unifier of Japan, Hideyoshi, launched major invasions of Korea in 1592 and 1597. When Western powers focused "gunboat" diplomacy on Korea in the mid-19th century, Korea's rulers adopted a closed-door policy, earning Korea the title of "Hermit Kingdom." Though the Choson dynasty recognized China's hegemony in East Asia, Korea was independent until the late 19th century. At that time, China sought to block growing Japanese influence on the Korean Peninsula and Russian pressure for commercial gains there. The competition produced the Sino-Japanese War of 1894-95 and the Russo-Japanese War of 1904-05. Japan emerged victorious from both wars and in 1910 annexed Korea as part of the growing Japanese empire. Japanese colonial administration was characterized by tight control from Tokyo and ruthless efforts to supplant Korean language and culture. Organized Korean resistance during the colonial era was generally unsuccessful, and Japan remained firmly in control of the Peninsula until the end of World War II in 1945. The surrender of Japan in August 1945 led to the immediate division of Korea into two occupation zones, with the U.S. administering the southern half of the peninsula and the U.S.S.R. taking over the area to the north of the 38th parallel. This division was meant to be temporary until the U.S., U.K., Soviet Union, and China could arrange a trusteeship administration.

In December 1945, a conference was convened in Moscow to discuss the future of Korea. A 5-year trusteeship was discussed, and a joint Soviet-American commission was established. The commission met intermittently in Seoul but deadlocked over the issue of establishing a national government. In September 1947, with no solution in sight, the United States submitted the Korean question to the UN General Assembly. Initial hopes for a unified, independent Korea quickly evaporated as the politics of the Cold War and domestic opposition to the trusteeship plan resulted in the 1948 establishment of two separate nations with diametrically opposed political, economic, and social systems. Elections were held in the South under UN observation, and on August 15, 1948, the Republic of Korea (R.O.K.) was established in the South. Syngman Rhee, a nationalist leader, became the Republic's first president. On September 9, 1948, the North established the Democratic People's Republic of Korea (D.P.R.K.) headed by then-Premier Kim Il Sung, who had been fostered and supported by the U.S.S.R.

Armistice negotiations began in July 1951, but hostilities continued until July 27, 1953. On that date, at Panmunjom, the military commanders of the North Korean People's Army, the Chinese People's Volunteers, and the UNC signed an armistice agreement. Neither the United States nor South Korea is a signatory to the armistice per se, although both adhere to it through the UNC. No comprehensive peace agreement has replaced the 1953 armistice pact.