Why were castle entrances small and limited in number?

In medieval military science, castle entrances were kept few and small to minimize the number of vulnerable points in the curtain wall that an attacker could exploit. Because gates represented the weakest link in a fortress's perimeter, limiting their size and number allowed defenders to concentrate their defensive efforts and resources more effectively.1

These entrances were heavily reinforced to prevent surprise entry and forced breaches. They were typically protected by barbicans—walled outworks that forced attackers into a confined, exposed space dominated by the castle's towers and walls. Furthermore, the passages were often deeply recessed and equipped with multiple defensive layers, including portcullises, heavy doors, and machicolations, which allowed defenders to drop missiles or substances on enemies below. By restricting the size and number of these entry points, architects ensured that the castle remained a formidable stronghold capable of withstanding direct assault.12