Heqin

historical practice of marrying Chinese princesses of emperors or minor branches of the ruling family to rulers of neighboring states

Heqin means marriage alliance. The term is used in Chinese history. An emperor would marry one of his princesses to his enemy. In return they would have peace with the enemy. It did not always work, and many people hated it.

Heqin
Traditional Chinese和親
Simplified Chinese和亲
Literal meaningpeace marriage