After successfully wrapping up his military campaign in Baekje by taking a considerable part of the southwestern kingdom, King Jangsu continued to pressure another kingdom of Silla in the southeastern part of the Korean Peninsula. As a result, he was able to expand his territory even further south. The king’s full-fledged southward policy is well described in a stone monument that still remains in present-day Chungju in the central region of Korea. The monument shows that Goguryeo occupied the entire middle section of the Korean Peninsula during the king’s reign.
Meanwhile, in the north, China was divided between the Northern and Southern Dynasties below the Yangtze River. At the same time a nomadic tribe called Yuyeon confronted the Northern Wei, which was one of China’s Northern Dynasties. Goguryeo developed multilateral diplomatic ties with China’s Southern Dynasty and Yuyeon as well as the Northern Wei. As a result, Goguryeo was able to maintain peace with northern states and tribes for a long time. Goguryeo didn’t wage war for nearly 200 years until 598. The long, peaceful period had never existed before and after King Jangsu.
It is challenging for any king to surpass his predecessor in terms of leadership. But King Jangsu continued to lead the golden period of Goguryeo, following his father King Gwanggaeto the Great. He governed his country differently from his father, but his achievements were as great as his father’s. The key to his success was his exceptional diplomatic skills, which shined brilliantly in complicated international politics in East Asia in mid-5th century.
In 414, the king set up a magnificent memorial stone at the site of his father’s tomb in Jilin Province, which is now in northeast China, in memory of the great accomplishments of his predecessor, King Gwanggaeto the Great.
King Jangsu died in 491 at the age of 97, after ruling his nation for 78 years. His posthumous name, Jangsu, means “long life.” During the long reign, the king made Goguryeo the largest state that had ever existed on the Korean Peninsula, with its territory stretching from Mongolia in the northwest to the middle section of the peninsula in the south.