Unlike granite or brick, coquina absorbed the impact of cannonballs rather than shattering. Attackers discovered that their artillery fire often embedded harmlessly into the stone, giving the fortress an unusual durability. Over the centuries, this property would prove crucial in the Castillo’s survival against repeated sieges.
The fort’s design followed the principles of the “bastion system” developed in Renaissance Europe. Its star-shaped layout with diamond-shaped bastions allowed defenders to cover all angles of approach with overlapping fields of fire. Thick walls, wide moats, and drawbridges reinforced the defenses, while casemates (vaulted rooms inside the walls) provided storage and shelter.
The First Major Test: English Siege of 1702
By the turn of the eighteenth century, St. Augustine was a contested frontier. The English colony of Carolina, founded in 1670, viewed Spanish Florida as a threat to its expansion. In 1702, during Queen Anne’s War, Carolina’s governor James Moore launched an attack on St. Augustine with a force of colonists and Native allies.
Moore’s army captured the town but could not breach the Castillo. The Spanish garrison and townspeople took refuge inside the fort, enduring a two-month siege. English cannon fire proved ineffective against the coquina walls. When Spanish reinforcements arrived by sea, Moore was forced to retreat, burning much of St. Augustine behind him.
This siege demonstrated the fort’s effectiveness and solidified its reputation as a nearly impregnable defense. It also underscored Spain’s determination to hold Florida, even as its empire weakened elsewhere. shutdown123