Harmony Between In-Laws

Abstract This article examines the entanglement of diplomatic marriages and rulership in the context of the royal marriages between the Koryŏ (918–1392) and the Mongol-Yuan (1271–1368) ruling houses. This perspective offers an answer to why and how the two ruling houses perpetuated their marriages for almost a century. This article argues that the incentive rested on the power of diplomatic marriages to restructure rulership and intermonarchical relationships. Yuan-Koryŏ royal marriages provided both rulers with new political resources to claim and maintain rulership. Meanwhile, in this new context, the Koryŏ king was but one among many in Koryŏ who shared personal-cum-political ties with the Mongol emperor, creating situations where rivals used these ties to challenge the Koryŏ king. Rulership involved more than asserting dominance; it was also about managing a ruler's myriad relationships and the political resources therein. This examination shows that marriage was not only an option in the diplomatic repertoire but also an influential component in rulership that required a ruler's meticulous management.