Baekje and Silla Retake the Han River
King Seong of Baekje and King Jinheung of Silla attacked Goguryeo together; Baekje took six districts on the lower Han and Silla ten on the upper river.

Kellnerp · CC BY-SA 3.0 · Source
By the mid-6th century Goguryeo was torn by aristocratic feuds over the throne, and the Türks were attacking from the north. In 551 King Seong of Baekje and King Jinheung of Silla seized the moment and attacked together.
Baekje recovered its old capital region, lost 76 years before — the six districts of the lower Han. Silla sent Geochilbu and seven other generals across Jungnyeong Pass to take ten districts on the upper river. Two years later Silla seized Baekje’s share too, breaking the alliance.