The polygonal fortress has several layers of defenses that protect the main Citadel, Fort St. George. Cannon are positioned at the Prince of Wales Bastion, outside the citadel walls, and of course within the fort itself. The fort is studded with firing positions, and a wooden bridge crosses over a dry moat that helps prevent direct attacks on the fortress walls.
During the Great Siege of Brimstone Hill in 1782, the fort protected the 950-man British garrison, local militia, and other residents from an attack by 8,000 French troops armed with 62 cannon, howitzers and mortars. The garrison held out for four weeks until the French cannon fire finally pierced the walls of the fortress, prompting an honorable surrender.