Korea, or 한국, is a territory located on a peninsula in East Asia. From 1897 until 1910, the peninsula was under the rule of the Korean Empire, which had replaced the centuries-old Joseon Kingdom. The Korean Empire aligned with Russia in the Russo-Japanese War, which ended with Japanese victory in 1905. This badly damaged relations between Korea and Japan, and in 1910 Korea was invaded and conquered by its stronger allied neighbor, bringing an end to the Korean Empire and well over half a millennium of sovereignty by Joseon monarchs. Korean resistance fighters fled the country in the face of the brutal oppression of the population, and during World War II they aligned themselves with the Allied Forces.
In 1945, the Soviet Union and the United States agreed on the surrender of Japanese forces in Korea in the aftermath of World War II, leaving Korea partitioned along the 38th parallel, with the north under Soviet occupation and the south under U.S. occupation. In 1948, as a consequence of the breakdown of relations between the USSR and the USA, two separate Korean governments were founded: the Republic of Korea, or South Korea, on the southern half of the peninsula, based nominally on the democratic republican model of the USA, and the Democratic People's Republic of Korea, or North Korea, on the northern half, based on the Stalinist system of the USSR.
From 1950 to 1953, the two Koreas, each with powerful international supporters, fought an inconclusive but costly war, which ended in a ceasefire and a slight adjustment of the border with a 2-km demilitarized zone providing a buffer on either side. The military situation on the peninsula has been tense ever since.
In the immediate aftermath of the war both countries endured severe poverty as well as political repression. Into the early 1960s, the North's socialist economy grew at a faster rate than its Southern counterpart, which was hampered by a vicious cycle of military dictatorship and political instability. The North's economic growth stagnated from the 1960s to the mid-1980s, and was sent into a severe tailspin by widespread crop failures in 1986. The Southern economy, meanwhile, gradually improved thanks in large part to integration into the global trade network existing among the US and its Cold War allies. As of 2014, nearly 97% of the peninsula's GDP is generated in South Korea.
Democracy in South Korea has grown steadily stronger since the Sixth Republic was established in 1987. Meanwhile, in the North the Korean Workers' Party and in particular its hereditary dictators, the Kims, have held to power by increasingly draconian methods, particularly since the early- to mid-1990s when many other communist governments fell to internal pressure for political reforms. In 2014 a report by Amnesty International concluded that human rights violations in North Korea are so severe and so widespread that a new category had to be created to categorize its dismal record.
South Korea has cultivated strong diplomatic relations with many countries around the world, and has come to be widely seen as a responsible diplomatic partner, as evidenced by the 2007 election of South Korean foreign minister Ban Ki-Moon as Secretary-General of the United Nations. However, the United States remains the Republic's most important trading partner and military ally. Meanwhile, North Korea has grown diplomatically isolated since the break-up of the Communist Bloc in the early 1990s. The People's Republic of China has stepped into the void left by the dissolution of the USSR and become North Korea's main supporter in the international arena. However, the PRC also opened diplomatic relations with South Korea in 1992, and has maintained cordial if not always warm relations with Seoul ever since.
Korea had been ruled by Japanese for three decades by the time of their entry into World War II. The Japanese contemptuously viewed Koreans as being nothing than "hewers of wood and drawers of water."  Many Koreans also lived in Hawaii, and up until the invasion, they made no secret of being glad they weren't part of the Empire to the Japanese residents of the islands. Some were police officers, a sight which many of the invading Japanese found disturbing and confirmed for them their belief that Americans were foolish.
Korea was rivaled only by Japan as an exporter of military electronics in the 22nd century. Korean technicians hired themselves out in a mercenary fashion to secret police forces across the world. One Korean helped the Palestinian security police in their vain attempt to capture four members of the Second Irgun.