Joseon had helped Ming China with ten…

Joseon had helped Ming China with ten thousand soldiers when she attacked the Manchus' Later Jin Dynasty under Nurhaci in 1619, but Korean General Gang Hong-rip had surrendered to Nurhaci, insisting that Korea held nothing against the Manchus and that she had sent reinforcements only to repay an obligation to the Ming Dynasty.

Korea's Westerners’ faction, which espouses explicit pro-Ming, anti-Manchu policies, had in 1623 deposed the realist King Gwanghaegun and installed King Injo.

In addition, the Ming Mobile Corps Commander Mao Wenlong is engaging in guerrilla warfare from his base on an island off the Korean peninsula.

The first Manchu invasion of Korea is triggered by Yi Gwal's rebellion against King Injo in 1624.

The revolt is soon crushed but remnants flee to Manchuria, and urge Nurhaci’s son Hong Taiji to invade Korea.