Military History of Goguryeo - Conflicts With Other Korean Kingdoms - Goguryeo–Baekje War

Goguryeo–Baekje War

Goguryeo and Baekje, two of the Three Kingdoms of Korea, considered themselves as the successors of Buyeo kingdom. King Onjo, the founder of Baekje, is said to have been a son of King Dongmyeongseong, founder of Goguryeo. However, the relationship between two kingdoms continued as an uneasy state.

King Geunchogo (346–375) further expanded Baekje's territory to the north through war against Goguryeo. In 369, Baekje was invaded by Goguryeo, but counterattacked in the Battle of Chiyang. In 371, the Baekje army of 30,000, led by Crown Prince Geungusu, took the fortress of Pyongyang and killed Gogugwon of Goguryeo. Goguryeo's territorial expansion also had been put on hold.

In 392, with Gwanggaeto the Great in personal command, Goguryeo attacked Baekje with 50,000 cavalry, taking 10 walled cities along the two countries' mutual border. This offensive infuriated Asin of Baekje and that king subsequently planned a counter-offensive against Gwanggaeto, a plan he was forced to abandon when his invasion force was defeated by Goguryeo 393. King Asin again attacked Goguryeo in 394, and was again defeated. After several heavy defeats, Baekje began to politically crumble and the leadership of Asin came under doubt. Asin lost to Goguryeo again in 395, and he was eventually pushed back to a front along the Han River, where Wiryeseong, then Baekje's capital city located in the southern part of modern day Seoul.

In the following year, Gwanggaeto led his huge fleet in an assault on Wiryeseong, approaching by sea and river. Asin was expecting a ground invasion and was caught with his defenses down. Gwanggaeto's forces burnt about 58 walled fortresses under Baekje control, and defeated the forces of King Asin. Asin surrendered to Gwanggaeto, even handing over his brother as a Goguryeo captive as condition for maintaining his own rule over Baekje. Gwanggaeto had finally gained superiority over its longtime rival Baekje on the Korean peninsula.

In 400, Silla requested Goguryeo assistance to defend against an alliance of Baekje-Gaya-Japanese allied forces, the Baekje kingdom to the west, and the Gaya Confederacy to the southwest. King Gwanggaeto responded with 50,000 troops, defeated both Japanese and Gaya cavalry units, and made both Silla and Gaya submit to his authority. In 401, he returned to King Silseong of Silla, to establish peaceful relationship between two kingdom while he continued the conquest of the north, but Goguryeo forces remained and continued to influence Silla.

In 433, Baekje and Silla formed an alliance (Hangul: 나제동맹, Hanja: 羅濟同盟) in response to the Goguryeo threat.

In 472, King Gaero of Baekje sent a letter to the emperor of Northern Wei. He stated that he was having trouble interacting with Wei because of frequent Goguryeo intervention, thus calling for military action against Goguryeo.

King Jangsu, eldest son of Gwanggaeto the Great, sought for the chance to invade the southern kingdoms of Korea, Baekje and Silla. As a result, King Jangsu secretly planned to attack Baekje. To disarm Baekje, he sent a Buddhist monk named Dorim. Dorim went to King Gaero's court, with the secret objective of corrupting the country before the invasion of Goguryeo. King Gaero began to favor Dorim, and played baduk with him every day, and the was able to talk Gaero into spending large sums of money on construction projects, which weakened the national treasury.

In 475, King Jangsu launched a full-scale invasion from both land and sea against the now politically unstable kingdom of Baekje. King Gaero was not at all prepared for the assault formulated by Goguryeo and King Jangsu. With momentum now in his favor, Jangsu then proceeded toward the capital and easily captured the city of Wiryesong, and slew King Gaero. Soon after, King Jangsu burnt the capital to the ground. Baekje moved its capital to Ungjin (present-day Gongju) to keep the kingdom alive. The war gave Goguryeo more or less total control of the Han River valley, the region essential to commercial and military power in the Korean Peninsula.

In 551, Baekje and Silla attacked the Goguryeo. The result of this allied attack on Goguryeo was the conquest of the Han river. In 553, Silla invaded Han River region and took the entire Han River region.

In mid-7th century, Gogureyo and Baekje formed an alliance (Hangul: 여제동맹, Hanja: 麗濟同盟) to territorial restoration, which was violated by Silla. The alliance had lasted until fall of Baekje in 660.