Focusing on the deployment of Goryeo troops to China in 1354, this chapter begins by tracing contemporary developments within the Yuan, which shaped the broader geopolitical environment in which the Goryeo regime operated. It then examines the choices Wang Gi and his court made when confronted with the largest military mobilization in East Asia in decades. The chapter concludes with a discussion of what the Yuan dynasty’s southern campaign likely revealed to Wang Gi and his advisers about military and political dynamics within the Great Khan’s realm and what they meant for the Goryeo court. This chapter’s narrative details convey a sense of dynamics within the Great Khan’s regime, which in turn sheds light on the Goryeo–Yuan alliance and Wang Gi’s place in the world.