How did effective cast-bronze siege cannon end the security of medieval curtain walls?

The development of effective cast-bronze siege cannon in the 15th century fundamentally compromised the security of medieval curtain walls by rendering their high, vertical stone structures highly vulnerable to battery.1

Prior to this, stone fortifications were designed to withstand traditional siege tactics like mining, battering rams, and escalade. However, these tall, thin walls could not withstand the kinetic impact of heavy bronze ordnance. The dramatic shift was exemplified during the 1494 French invasion of Italy, where superior artillery breached the fortress of Monte San Giovanni in just eight hours—a site that had previously resisted a seven-year siege. Similarly, the Ottoman Empire utilized large bombards to breach the walls of Constantinople in 1453, signaling the end of the medieval era of fortification.21

This sudden vulnerability forced a revolution in military architecture. Engineers moved away from high, vertical masonry toward low, thick, earthen-backed ramparts and bastions that were far more resistant to cannon fire. This transition marked the definitive end of the medieval castle as a primary defensive stronghold and the beginning of modern military fortification.13