The Amasya Treaty (1555) ended a half-century of Ottoman-Safavid military and ideological rivalry during the sixteenth century. My paper focuses on why the Ottoman and Safavid empires made this treaty despite a long-standing ideological and political divide. It has been widely held that the Safavids could not afford such a costly rivalry and, tired of the Ottoman military campaigns, they pleaded with the Ottomans to make peace. Based on my comparative research in Ottoman, Persian, and European sources, I find that this narrative misses many essential points and omits certain historical facts just before the treaty was signed. I argue that the Ottomans also wished for and, at once, requested peace with the Safavids. I show that, although the Ottoman army ostensibly left Istanbul to fight with the Safavids in 1553, the primary motive was to use warfare as a diplomatic tool to force the Safavids to ask for peace.