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.