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How did gunpowder artillery make medieval castles more vulnerable?

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tactics Sumerian phalanx, a block of foot soldiers depicted standing shield-to-shield, presenting spears, and advancing in a dense mass, detail from the Stele of the Vultures, limestone bas-relief, c. 2450 bce; in the Louvre Museum, Paris.

The development of effective cast-bronze siege cannon in the 15th century fundamentally undermined the security of medieval curtain walls, which had previously been considered nearly inviolable.1

Before this advancement, high, vertical stone walls provided excellent protection against traditional siege methods like escalade. However, the introduction of heavy artillery allowed besiegers to breach these structures with unprecedented speed and force. For example, French forces in 1494 breached the fortress of Monte San Giovanni in just eight hours, a site that had previously withstood a seven-year siege. Similarly, the use of large bombards by Mehmed II to shatter the walls of Constantinople in 1453 demonstrated the devastating impact of gunpowder technology on traditional fortifications.21

Because medieval walls were high and vertical, they were highly susceptible to battery fire. This vulnerability forced a revolution in military engineering, leading to the adoption of lower, thicker walls, earthen ramparts, and the bastioned trace, which were designed to better withstand or deflect the impact of cannon shot.13