Thirty cannons were mounted by the Bastille’s defenders during the storming on 14 July 1789.
The fortress held 18 eight-pound guns and 12 smaller artillery pieces, making 30 cannons in total. Its garrison consisted mainly of 82 Invalides—veteran soldiers—and 32 Swiss grenadiers from the Salis-Samade Regiment. The Bastille’s artillery was positioned to defend its towers, walls, gates and approaches.
The attackers were primarily Parisian civilians seeking gunpowder and weapons, but they were joined by mutinous French Guards and brought five cannons of their own. Those guns were used against the fortress’s wooden gate and helped turn the confrontation into a genuine siege. The Bastille surrendered after several hours of fighting, with the garrison unable to endure a prolonged attack.
A common mix-up is to confuse the defenders’ 30 guns with the attackers’ five. The fortress’s cannon total also does not mean all 30 were fired effectively: the Bastille’s walls gave its soldiers a strong defensive position, but poor leadership, limited supplies and the arrival of trained attackers weakened its resistance.