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Goguryeo also later known as Goryeo, was a Korean kingdom which was located on the northern and central parts of the Korean Peninsula and the southern and central parts of modern-day Northeast China (Manchuria). At its peak of power, Goguryeo conquered most of the Korean Peninsula and large parts of Manchuria, along with parts of eastern Mongolia, Inner Mongolia, and modern-day Russia. Along with Baekje and Silla, Goguryeo was one of the Three Kingdoms of Korea. It was an active participant in the power struggle for control of the Korean peninsula and was also associated with the foreign affairs of neighboring polities in China and Japan. The Samguk sagi, a 12th-century text from Goryeo, indicates that Goguryeo was founded in 37 BC by Jumong, a prince from Buyeo, who was enthroned as Dongmyeong. Goguryeo was one of the great powers in East Asia, until its defeat by a Silla–Tang alliance in 668 after prolonged exhaustion and internal strife caused by the death of Yeon Gaesomun. After its fall, its territory was divided between the Tang dynasty, Later Silla and Balhae. The name "Goryeo", a shortened form of Goguryeo (Koguryŏ), was adopted as the official name in the 5th century, and is the origin of the English name "Korea".