Reign

He attempted to strengthen royal control of the aristocracy, by selecting officials from his own Buyeo clan, at the expense of the powerful Hae and Jin clans.

In 469, he ordered a surprise attack in which the city of Cheongmongnyeon (청목령, 靑木嶺 ; near modern Kaesong) was retaken from Goguryeo. In 472, he sent an embassy bearing tribute to Northern Wei requesting support against Goguryeo』s attacks. However, these advances were rebuffed by the Wei court, which tried to avoid war with Goguryeo which had greater military power at the time, while fighting against Southern Dynasties.

In the early 470s, according to the Samguk Sagi, King Jangsu of Goguryeo sent a Buddhist monk named Dorim, who was actually a Goguryeo agent. Dorim used Gaero』s passion for the game of baduk to ingratiate himself, and persuade the king to neglect the country』s defense in favor of public works.

Fall of the capital

In 475, Jangsu launched an attack with 30,000 men and overran Baekje』s defenses in seven days, taking the Han River valley including the capital. Gaero was taken to Acha Mountain Fortress and slain by two men who had defected to Goguryeo from Baekje. Baekje's ally Silla sent an army of 10,000, but arrived too late.

He was the last to rule Baekje from its historic heartland in the Han River valley. After his death, Hae Gu, of the suppressed Hae clan, led a bloody revolt.

Family

• Father: Biyu of Baekje

• Mother: unknown

　• Queen: unknown

　　• Buyeo Modo (扶餘牟都, ?–477) – 22nd King of Baekje, Munju of Baekje.

　　• Buyeo Gonji (餘餘昆支, ?–477) – military commander and father of 24th King of Baekje, Dongseong of Baekje. He was sent to Japan in 461 where he had a son with a Japanese woman.

治世

蓋鹵王在位期間，通好于中國南朝宋，與新羅，倭國結盟，以抗高句麗。努力維持百濟傳統的外交政策。後來招引北魏討伐高句麗未遂，蓋鹵王因此惹禍上身。475年，高句麗攻破百濟首都慰禮城，蓋鹵王被殺。

對南朝宋通好

457年（大明元年）10月，蓋鹵王接受南朝宋皇帝劉駿「鎮東大將軍」的封號，與宋結好。並于471年向宋朝貢。

與倭國結好

461年，遣弟軍君昆支往倭國為人質，與倭國通好。

與北魏的接觸

百濟自近肖古王以來一直與南朝通好。蓋鹵王時，開始試圖通過與北魏的接觸來牽制北方強敵高句麗。472年（北魏延興2年），蓋鹵王向北魏上表，聲稱高句麗一直在欺壓百濟，希望北魏加以討伐。但北魏與南朝宋的戰事正酣，無意與當時以逐漸崛起的高句麗爆發全面軍事對抗，僅僅派出邵安為使者，前往調查情況，並斥責高句麗。

與高句麗的關係（百濟的衰亡及高句麗的進攻）

469年，蓋鹵王認為百濟的軍事實力已足夠強大，率軍突襲高句麗，並奪回被高句麗侵佔的青木嶺（今開城附近）。僧人道琳在高句麗長壽王的授意下，前往百濟會見蓋鹵王。道琳以其精湛的棋藝成功得到了蓋鹵王寵倖。在道琳的勸說下，蓋鹵王挪用大量軍費修建佛寺，以致於國庫空虛。道琳秘密向長壽王報告了百濟國內的現狀。475年9月，長壽王趁機率領三萬大軍討伐百濟。蓋鹵王遣其子文周往新羅求救，新羅王慈悲麻立幹遣一萬人來支援百濟，但為時已晚。百濟首都慰禮城被高句麗攻陷。蓋鹵王出奔，並在阿且城（今首爾特別市城東區康壯洞）被殺死。