Korea is a geographic area, civilization, and former state situated on the Korean Peninsula in East Asia. Korea is currently divided into North Korea and South Korea.

Although the borders of historical Korean dynasties fluctuated, the peninsula today is defined as coterminous with the political borders of the two Koreas combined. Thus, the peninsula borders China to the northwest and Russia to the northeast, with Japan situated to the southeast across the Korea Strait.

The history of Korea began with the legendary founding of Gojoseon in 2333 BC by Dangun. Limited linguistic evidence suggests probable Altaic origins of these people, whose northern Mongolian Steppe culture absorbed immigrants and invaders from northern Manchuria, Mongolia and China. The adoption of the Chinese writing system ("hanja" in Korean) in the 2nd century BC, and Buddhism in the 4th century AD, had profound effects on the Three Kingdoms of Korea. Koreans later passed on these, as well as their own advances, to Japan.

After the unification of the Three Kingdoms by Silla in 676, Korea was ruled by a single government and maintained political and cultural independence until the nineteenth century[citation needed], despite the Mongol invasions of the Goryeo Dynasty in the 13th century and Japanese invasions of the Joseon Dynasty in the 16th century. In 1377, Korea produced the Jikji, the world's oldest movable metal print document. In the 15th century, the turtle ships, possibly the world's first ironclad warships, were deployed, and during the reign of King Sejong the Great, the Korean alphabet han-geul was created.

During the latter part of the Joseon Dynasty, Korea's isolationist policy earned it the Western nickname the "Hermit Kingdom". By the late 19th century, the country became the object of colonial designs by the imperial aggressors of Japan and Europe. In 1910, Korea was forcibly annexed by Japan and remained occupied until the end of World War II in August 1945.

In 1945, the Soviet Union and the United States agreed on the surrender and disarming of Japanese troops in Korea; the Soviet Union accepting the surrender north of the 38th parallel and the United States taking the surrender south of it. This led to division of Korea by the two great powers, exacerbated by their inability to agree on the terms of Korean independence. The two Cold War rivals then established governments sympathetic to their own ideologies, leading to Korea's current division into two political entities: North Korea and South Korea.

Source : http://en.wikipedia.org