In 1577, six years after Philip II's victory over the Turks at the Battle of Lepanto, Pope Gregory XIII called Europe's final crusade in an attempt to press home Christendom's recent triumph over its Islamic nemesis. From the eleventh century, the institution of the Crusade had embodied Latin Christendom's spiritual unity, as well as demonstrating the Church's power to mobilise the European nobility in the service of Holy War. While Jerusalem had long since been lost, the crusading spirit was far from dead as Europe entered the modern age. The Turkish conquest of Constantinople in 1453 had signalled the emergence of a powerful new threat to Christendom on her eastern doorstep, while the completion of the Spanish Reconquista in 1492 marked a parallel resurgence of Christendom in the western Mediterranean. By the latter half of the sixteenth century, the continuing proximity of the Turkish threat, combined with the religious fervour of the Counter-Reformation and the waxing of Spanish power all suggested scope for a renewed Holy War against the Ottomans.

That the pope ultimately failed to rally Christendom for a new crusade is illustrative of the final collapse of Christian unity and of Latin Christendom's disintegration as a viable international order by the late sixteenth century. Far from pressing home his advantage against the Ottomans after Lepanto, Philip instead made peace with the sultan in 1578 so as to pursue the more urgent task of crushing Calvinist rebels in the Spanish Netherlands.