Frustrated by siege warfare, Saritai instead used his armies' superior mobility to bypass the Goryeo army and succeeded in taking the capital at Gaesong. Elements of the Mongol army reached as far as Chungju in the central Korean peninsula; however, their advance was halted by a slave army led by Ji Gwang-su where his army fought to the death. Realizing that with the fall of the capital Goryeo was unable to resist the Mongol invaders, Goryeo sued for peace.