While the Europe-wide cultural impact of the fall of Constantinople to Sultan Mehmed II is well known, its political reverberations in the Holy Roman Empire have received comparatively little attention. This article argues that the events of 1453 inaugurated a new dynamic in the empire that facilitated the polity's consolidation and the creation of new collective institutions within it long before Maximilian I (1486–1519), whose reign is often presented as a constitutional turning point. Some prince-electors had been calling for more effective peace-keeping and judicial institutions for decades before 1453 but lacked the leverage to compel kings and emperors of the Romans to accept political change on their terms. The fall of Constantinople provided a focal point for these negotiations: in return for promising to support an anti-Ottoman crusade, the reformists were able to force a compromise on new peace-keeping legislation at the diets of the 1450s and 1460s. This compromise was catalyzed by public pressure. There was a widely held expectation that leading imperial protagonists should fulfill this mission to defend Christendom, manifested in orations, diplomatic missives, poetry and songs, plays, and early printed pamphlets produced within and for a range of German-speaking public spheres.