Silla–Baekje Alliance

King Biyu of Baekje and Nulji Maripgan of Silla allied against Goguryeo's southward push.

Since Gwanggaeto’s day Silla had lived under Goguryeo’s interference, and Baekje had lost its lands north of the Han. When Jangsu moved his capital to Pyongyang in 427 and pressed south, King Biyu of Baekje sent envoys to Silla in 433 seeking peace, and Nulji Maripgan agreed.

Each sent troops when Goguryeo attacked the other; in 475 Silla dispatched 10,000 men to Hanseong, too late to save it. In 493 King Dongseong of Baekje married the daughter of the Silla noble Biji, sealing a marriage alliance.

In 551 the two kingdoms together retook the Han River basin from Goguryeo. But in 553 Silla’s King Jinheung seized Baekje’s share of the lower Han, ending the 120-year alliance, and the battle of Gwansan Fortress the next year made them bitter enemies.