In 1224, a Mongol envoy was killed in obscure circumstances and Korea stopped paying tribute. Ögedei dispatched Saritai to subdue Korea and avenge the dead envoy in 1231. Thus, Mongol armies began to invade Korea in order to subdue the kingdom. The Goryeo King temporarily submitted and agreed to accept Mongol overseers. When they withdrew for the summer, however, Choe U moved the capital from Kaesong to Ganghwa Island. Saritai was hit with a stray arrow and died as he campaigned against them.