The combined operation that captured Fort San Luis

The Bocachica defense centered on Fort San Luis, with 49 cannon, three mortars, and about 300 troops. A boom stretched from Isla de la Bomba toward Fort San José, while six Spanish ships and the smaller fort's guns reinforced the channel. The British first landed 300 grenadiers at night to secure the beach before reinforcing in daylight. Grenadiers were selected as tall, strong soldiers suited to handling grenades and leading an intimidating assault. Keeping the advance party small reduced the risk of losing a larger body among rocks and difficult approaches in darkness, while securing the beach before defenders could oppose a daylight landing. Their sole engineer spent two weeks preparing a 24-pounder battery, while ships under Commodore Richard Lestock absorbed the fort's attention and heavy damage. That naval fire allowed the shore guns to establish themselves and create a breach; Spanish forces then withdrew, some ships were scuttled, and Fort San Luis fell. The works and fighting removed roughly 970 more British troops through death, wounds, or hospitalization before the force entered the bay. The success therefore came at substantial cost and reduced the effective landing force before the decisive inner assault.