Despite a brief 61 years on the world stage, North Korea has constantly posed a challenge to U.S. policy makers as the small communist country struggles to define its global position.

After the Allied victory in World War II, the victorious powers decided to split Korea in half, giving the Soviet Union control north of the peninsula's 38th parallel while a United States military administration governed the south.

In the North, Soviet-backed leader Kim Il Sung established a Stalinist regime based solidly in the communist tradition. His North Korean People's Army was well equipped with Soviet military tanks and weapons. Meanwhile, U.S. generals backed a staunch anticommunist leader, Syngman Rhee, as South Korea's first president. Following the two superpowers' division of the peninsula, there was palpable tension between the two Koreas.

The Korean War
On June 25, 1950, the North Korean Army invaded the South with the aid of Soviet military advisers and supplies — ostensibly to reunify the peninsula under Kim's communist regime.

Advancing quickly against ill-equipped South Korea, the North Korean forces overran Seoul three days into the invasion. In response, the United States called on the United Nations to name the North as aggressors and authorize an international military response in the South's defense.

The U.N. Security Council condemned the North's attack, and a U.S.-led international defense force was dispatched to defend South Korea. As the Soviet Union was boycotting the Security Council at the time, they could not veto the decision that would affect its long-time ally.

U.S. troops in the region were quickly deployed to repel the North Korean incursion, but had limited success fighting the better-prepared communist army. U.N. and U.S. forces were forced to retreat to the southern part of the peninsula to regroup.

U.S. General Douglas MacArthur and a larger U.S.-led international military coalition conducted a daring amphibious assault at the port of Inchon, near Seoul, on September 15, 1950.

In the well-planned counterattack, U.S. forces cut off communications and supplies to the North's forces just below the 38th parallel, barricading North Korean troops inside South Korean territory.

U.N. and U.S. forces already positioned in the southern region of Pusan launched a new assault on the North. Overwhelmed and cut off from reinforcements, North Korea's troops relinquished control of Seoul to U.N. forces on September 26.

After recapturing the South, U.N. forces pursued the North's retreating troops across the 38th parallel. The joint forces, under General MacArthur, captured Pyongyang in mid-October and advanced north, toward the China border.

Communist China repeatedly warned they rejected the presence of U.N. troops in North Korea, saying they would launch their own offensive if the incursion continued. U.S.-led forces continued to advance.

Roughly 300,000 Chinese forces were amassed at the border to stave off further advance and defend North Korea. Media accounts from the time said General MacArthur wanted to attack bases in China, but U.S. President Harry Truman, fearing the start of World War III, ordered him not to continue.

Finally in November, Chinese forces crossed the border and overwhelmed the American-led troops. Aided by Chinese "volunteer" soldiers, the North retook Pyongyang on December 6, 1950. But soon after, the war slowed to a stalemate. Some two-and-a-half years later, all sides reached an armistice in July of 1953.

By the time the armistice was signed, some four million Korean soldiers and civilians had been killed. Although there are conflicting reports on the number of casualties, Korean specialist and historian Bruce Cumings of the University of Chicago estimates the North lost around 2.5 million people, and the South endured the loss of up to 1.5 million soldiers and civilians. Cumings estimates that up to 70 percent of civilians were among the war dead.

According to the U.S. Department of Defense's recently revised figures, between 33,000 and 37,000 American soldiers lost their lives during the Korean War. Other U.N. casualties were estimated at more than 15,000, while Chinese casualties totaled more than one million, Cumings said.

At the end of the war, the U.S. levied economic sanctions against North Korea, a move that would have long-term effects on the North's economy and its ability to trade in the world market.

-- Compiled by Maureen Hoch for the Online NewsHour