Japanese Emperor Hirohito announced his country's surrender to Allied forces in August 1945, shortly after the U.S. dropped atomic bombs on the cities of Hiroshima and Nagasaki. As part of the surrender terms, Japan was forced to drop its claim to Korea, ending 35 years of colonial rule.

That December, foreign ministers from the Soviet Union, the U.S. and Great Britain assembled to craft a provisional post-war government for Korea. The plan -- solidified during the Yalta and Potsdam conferences in 1945 -- involved temporary multinational "trusteeship" of Korea by China, Britain, the U.S.S.R. and the United States, lasting no longer than five years.

Worried that the Soviets may try to take over the entire peninsula, the United States proposed dividing the region along the 38th parallel into two zones. The Soviets agreed to the order, which became known as the State Department's General Order No. 1. The United States promptly stationed 25,000 of its troops, led by Gen. Douglas A. MacArthur, in the southern half.

The division was intended as a temporary solution until the multinational "trusteeship administration" was put in place. However, after the Soviets and the United States failed to reach an agreement for the trusteeship, the intended temporary division became the de facto arrangement for more than 50 years.

Koreans on both sides of the 38th parallel were not happy with the situation. In the north, the Korean Workers Party used anti-imperialist rhetoric to attract millions of poor peasants with no prior political experience.

To the south, Korean nationalists vehemently opposed the trusteeship arrangement, demanding their right to self-governance. As an alternative to the trusteeship, Korean leaders proposed the Committee for the Preparation of Korean Independence and set up municipal offices, or People's Committees, throughout the country to take control of the government.

In 1945, the CPKI announced the formation of the Korean People's Republic, also called the Choson Inmin Konghwaguk, along with an agenda to nationalize Japanese-owned banks and businesses.

The CPKI's agenda was antithetical to U.S. plans to "bolster the status quo and resist radical reform of colonial legacies," according to the U.S. Library of Congress Web site.

The United States also "tended to interpret resistance to United States desires in the south as radical and pro-Soviet."

The CPKI fell apart when the U.S. Army Military Government prohibited CPKI meetings, fearing that it had been infiltrated by the communists, according the Library of Congress.

"When Korean resistance leaders set up an interim 'people's republic' and people's committees throughout southern Korea in September 1945, the United States saw this fundamentally indigenous movement as part of a Soviet master plan to dominate all of Korea. [I]t immediately became wrapped up with United States-Soviet rivalry, such that the Cold War arrived early in Korea -- in the last months of 1945," the Library of Congress explained.

Suppression of the people's committees provoked several uprisings and protests against the United States, which Koreans interpreted as a continuation of colonial rule.

In 1946, world leaders convened to meet with Korean officials expecting to finalize the trusteeship administration. The plan stalled, however, after the Soviets refused to include non-communist Koreans in a proposed provisional government. The U.S. protested on the basis it would result in an interim Korean government headed only by communists.

By 1947, the U.S. abandoned efforts to continue talks with the Soviets to consolidate a multilateral trusteeship administration for the Korean peninsula.

Instead, the United States decided to seek U.N. backing for U.S. policy in Korea and ask the United Nations to supervise plebiscite for all of Korea -- provided that the Soviet Union would cooperate -- and in southern Korea if the Soviets rejected the plebiscite.

The Soviets and North Korea refused the U.N.-supervised plebiscite.

Consequently, the South held its own general elections. Syngman Rhee -- an influential anti-communist political leader from the south -- became South Korea's first president, ushering in the Republic of Korea, or the Daehanminguk, on May 10, 1948.

Shortly afterwards, on Sept. 9, 1948, the North established a socialist-styled government, called the Democratic People's Republic of Korea, or the Joseon Minjujuui Inmin Gonghwaguk, and declared Kim Il Sung, a 34-year-old Soviet army recruit and member of the Chinese Communist Party, as its premier.

Kim was already a popular hero to Korean nationalist-communist groups, and he was widely known for leading the anti-Japanese struggle during Korea's colonial period. He belonged to a group of highly nationalistic Korean guerrillas determined to keep Korea independent from any superpower. Nonetheless, North Korea maintained close ties with the Chinese Communist Party and the Soviets. During this time, the Soviets provided weaponry to the North Koreans.

U.S. officials dismissed Kim Il Sung as a communist puppet-leader serving the Soviets, especially after the Soviets refused to allow the U.N. to observe North Korea’s general elections.

Syngman Rhee and Kim Il Sung claimed their respective regimes were the sole legitimate government on the peninsula, and each perceived the other as the main impediment to unifying the nation.

As leaders of diametrically opposed governments, Syngman and Kim sought to incite hostility towards the other, calling upon their people to crush the other government.

Ultimately, these political tensions exploded into a multinational three-year war in 1950.

-- Compiled by Liz Harper for the Online NewsHour