King Taejong-Muyeol the Great of Silla (Born: 604 – Died: June 661), whose born as Kim Chun-chu (김춘추/金春秋), was the 29th monarch of the southern Korean kingdom of Silla and Final Ruler of Pre-Sillan Unification, ruled from 654 to 661. As a member of the Royal House of Gyeongju Kim, he is credited for leading the unification of the Three Kingdoms of Korea. He was a friend of Kim Yu-shin - great-grandson of ex-King Guhyeong-Guhae of Geumgwan Gaya (Royal House of Gimhae Kim), who eventually became his brother-in-law after he married the latter's sister.
King Taejong-Muyeol was born with the "sacred blood" rank of seonggol. His father, Kim Yong-su (김용수/金龍樹), was a son of Silla's 25th ruler, King Jinji. When King Jinji was overthrown, all royalty from his line, including Kim Yong-su, were deemed unfit to rule over the kingdom. However, as he Yongsu was one of the few remaining seonggols, and married a seonggol princess (King Jinpyeong's daughter Princess Cheonmyeong), their child, Kim Chun-chu, became seonggol and thus had a claim to the throne. Kim Yong-su was a powerful figure in the government.
However, he lost all of his power to Kim Baek-ban, the brother of the king. In order to survive, he had accepted to become a jingol, the rank that was right below seonggol. Therefore, he lost his chance of becoming the king, and so did his child, Kim Chun-chu. Following the death of his aunt, Queen Seondeok, Chunchu was passed over in favor of Queen Jindeok of Silla, the last verifiable seonggol. With her death, all the seonggols were dead, so somebody with the royal blood in the jinggol rank had to succeed the throne.
Kim Alcheon (a.k.a. So Alcheon), who was then Sangdaedeung (highest post of government) of Silla was the original favorite to succeed the throne. His father was a seonggol, who married a jingol wife so that his son would not be a seonggol and suffer from the fight for the throne. However, Kim Yu-shin supported Kim Chun-chu, and Alcheon eventually refused the throne and supported Chun-chu's claim. As a result, Kim Chunchu succeeded the throne as King Taejong-Muyeol the Great.
He was well acquainted with the Emperor Gaozong of the Tang Dynasty, for he and the Emperor were friends before Gaozong became an Emperor. King Muyeol was a great support to the Emperor, and the Emperor returned the support to King Muyeol. He constantly pleaded with the Tang for reinforcements to destroy Baekje, to which the Tang finally acquiesced in 660, sending 130,000 troops under General Su Dingfang. Meanwhile, Kim Yushin set out from Silla with 50,000 soldiers and fought the bloody Battle of Hwangsanbeol leaving Baekje devastated and unprotected. King Uija of Baekje finally surrendered, leaving only Goguryeo to face Silla as an adversary on the Korean peninsula.
In June 661, King Taejong-Muyeol the Great died, leaving his son Kim Beop-min to assume the throne as King Munmu the Great. King Munmu the Great played his pivotal role in Sillan Unification after defeating Goguryeo which led by King Bojang in 668 CE. King Taejong-Muyeol was buried at Seoak-dong 842-beonji, Gyeongju, Northern Gyeongsang - near to Seoak-dong Tumuli Site and Royal Tomb of King Heon-an, 47th Monarch of Silla Kingdom.