There was an Khitan invasion August 14th in 1216. After that, Kim Chwi-ryeo was appointed Hugunbyeongmasa and he distinguished himself in War. Although Vanguard of Khitan came southward fiercely, thanks to his trying, Goryeo could drive them away Cheongsaejin by blocking them in Joyangjin and Hyangshan battles. Subsequently the battle with Khitan’s Hubaldae became more fierce. When Goryeo army’s strength fell because of previous battles, Kitan’s Hubaldae constantly came southward with expanding its front to Gaegyeong and Central region getting across Cheongcheon and Daedong Rivers. Their southward movement was considered that not only they could secure the foundation for building up a nation but also they tried to get out of the range of Jin Dynasty and Mongolia. It was Kim Chwi-ryeo’s Maekgok and Bakdalhyeon battles that stopped this southward advance. The road which connects Wonju and Chungju were important military strategic point which was able to get to Gyeongsang-do region. The primary perimeter was the Maekgok battle. The victory at the Maekgok battle could induce Hubaldae to come Bakdalhyeon where it was a road to go from Jeju to Chungju area. Also the triumph at the Bakdalhyeon could throw them out Myeongju region. Yet because Goryeo did not completely suppress invaders, since then, it made it possible for Hubaldae to move to Yeojin land passing by Donggae area. As a result, the war kept continuing because Vanguard appeared on Bukgae and Hubaldae appeared on Donggae. Meanwhile, the Khitan’s retreat from the Yeojin land gave Dongjin Country where were in Yeojin an excuse to intrude Goryeo. Eventually it became the opportunity for Mongolia and Dongjin to invade Donggae region. Although the allied powers claimed that it was a pretext for sweeping Khitan, it brought about another critical situation to Goryeo. It was Kim Chwi-ryeo who took the important role to overcome this crisis. He understood Mongolia’s intent and by active responding, completely mopped up the remainders of Khitan in the Gangdongseong battle. After all, by establishing ‘A Pact of Brotherhood’ between Goryeo and Mongolia, Goryeo could overcame the new war crisis. Finally ‘Pact of Brotherhood’ meant not only finishing long war with Khitan but also leading the consequence to make a new external environment with Mongolia. However we should remember this Pact because it played an important role to lead beneficial aspects for Goryeo dynasty in the process of war and negotiation with Mongolia.