Jangsu of Goguryeo

Jangsu (394–491, r. 412–491) was the 20th monarch of Goguryeo, the northernmost of the Three Kingdoms of Korea. He was born in 394 as the eldest son of Gwanggaeto. He became the crown prince in 409, and upon his father's death in 412, became the ruler at the age of 18.

Jangsu reigned during the golden age of Goguryeo, when it was a powerful empire and one of the great powers in East Asia. He continued to build upon his father's territorial expansion through conquest, but was also known for his diplomatic abilities. Like his father, Gwanggaeto the Great, Jangsu also achieved a loose unification of the Three Kingdoms of Korea. In addition, Jangsu's long reign saw the perfecting of Goguryeo's political, economic and other institutional arrangements. He is also noted for building the Gwanggaeto Stele, dedicated to his father. Jangsu's posthumous name means "Long Life", based on his longstanding reign of 79 years until the age of 97,

During his reign, Jangsu changed the official name of Goguryeo (Koguryŏ) to the shortened Goryeo (Koryŏ), from which the name Korea originates.

Family

Father: King Gwanggaeto ()
Grandfather: King Gogukyang ()
Unknown wife
Son: Prince Joda/Juda (); father of King Munja.
Son: Prince Seungu ()
Unnamed daughter

Early reign

During his early reign, Jangsu dedicated much of his efforts toward stabilizing an empire that had experienced great and sudden growth as a direct result of his father's conquests. Jangsu built a magnificent tomb for his father, Gwanggaeto the Great, and along with it an imposing tombstone engraved with his father's accomplishments (now known as the Gwanggaeto Stele).

In 427, he transferred the Goguryeo capital from Gungnae Fortress (present-day Ji'an on the China-North Korea border) to Pyongyang, a more suitable region to grow into a burgeoning metropolitan capital, which led Goguryeo to achieve a high level of cultural and economic prosperity.

Relations with Chinese dynasties and nomadic states

When Gwanggaeto the Great ruled Goguryeo, the Chinese mainland was dominated by five non-Han Chinese peoples and divided into multiple states. During Gwanggaeto's time, Goguryeo invaded Later Yan and conquered Liaoning, but when Jangsu came to the throne, the chaos in northern China was coming to an end. However, Northern Yan's existence was threatened by the powerful Xianbei Tuoba clan of Northern Wei to the west, compelling Northern Yan to make an alliance with Goguryeo, its neighbor to the east. Hence, Jangsu turned his military ambitions southward toward the Korean peninsula. Jangsu again encouraged Liu Song to invade Northern Wei in 459 when he sent loads of crossbows and provided gold and silver. The Northern Wei government was upset by Jangsu's actions but had to keep peace with Goguryeo to continue its war against Liu Song and the Rouran Khaganate.

Jangsu also maintained contact with Northern Wei, and the two empires established a formal relationship in 435. This relationship proved to be useful when Goguryeo waged war against Baekje, which had secretly sought a military alliance with Northern Wei against Goguryeo, After securing peace with the Rourans, Jangsu invaded the Khitans, a branch of the Xianbei confederacy at the time, and then attacked the Didouyu with his Rouran allies.

After the Khitans surrendered to Goguryeo, Jangsu sent gifts to both Northern Wei and Southern Qi, which took over the southern half of China after overthrowing Liu Song in 479. but the frequency started to drop since Jangsu continued to keep hospitality with Qi. This decrease in exchanged delegates outraged Emperor Xiaowen, and at last he gave an order to capture Goguryeo delegates before they could reach the Qi capital. However, Jangsu paid no mind, and continued to send delegates to Qi. Northern Wei could not block Goguryeo, which indicated the success of Jangsu's diplomatic strategy: maximizing the situation and manipulating the power struggles between rival Chinese states to Goguryeo's advantage.

Gaya

Gaya found itself in a precarious situation due to its geographical disadvantage of being sandwiched by Baekje and Silla, and ultimately could not develop into an advanced nation.

Baekje campaign and Dorim

In 472, Gaero, the ruler of Baekje, sent a letter to the emperor of Northern Wei, stating that he was having trouble interacting with him due to frequent Goguryeo intervention, thus calling for military action against Goguryeo. However, Baekje failed to get its emissary back and was unable to receive the military support of Northern Wei. In response, Jangsu secretly planned to attack Baekje, which despite its losses against Gwanggaeto the Great, still held a significant power base in the Korean peninsula. In order to disarm Baekje, he sent a Buddhist monk named Dorim,

In 475, Jangsu launched a full-scale invasion from both land and sea against the now politically unstable kingdom of Baekje. Dorim was successful in gaining information about Baekje, Soon after, Jangsu burned the capital to the ground, along with several other cities that he conquered from Baekje. Henceforth, Baekje had no choice but to move its capital to mountainous Ungjin (present-day Gongju), 80 miles to the south, which provided a natural protection for the devastated kingdom. To secure the allegiance of his de facto protectorate, Jangsu demanded the younger brother of King Nulji of Silla to become a political hostage. King Nulji broke off relations with Goguryeo in 454. Jangsu invaded Silla in 468, expanding his domain into parts of Gangwon Province, and again in 489, capturing 7 walled cities and expanding his domain into parts of North Gyeongsang Province. With his victory over Silla, Jangsu erected a stone monument in present-day Chungju, praising the accomplishments of his father and himself. This monument remains at the same site, holding historical importance as the only surviving Goguryeo stele in the Korean peninsula.

Death and legacy

King Jangsu died in 491, at the age of 97. His temple name means "Long Life" in hanja. During his reign, Goguryeo was at its golden age, includes Jangsu as a selectable hero of the Korean civilization.

Portrayed by Jung Yoon-seok in the 2007 MBC TV series The Legend.