Let’s get this out of the way right from the start. At the heart of this piece is a massacre, a bloody mass murder executed in a scorching swamp as empires fought to assert their dominance in the New World. The initial body count was in the hundreds, inflicted over nationalistic fervor and minor religious differences. Even so, it is the background for one of my favorite forts, a small outpost in a coastal salt marsh that was set up to guard a Florida city’s back door.

Today, 450 years later, the blood had dissipated. Visitors to Fort Matanzas take a pleasant boat ride from the parking lot to sun-drenched Rattlesnake Island and climb a set if wooden steps to the stone gun deck. Underneath the platform is a cistern to capture fresh rainwater (the surface water being too brackish to drink), and at one end stands a square tower that holds barracks, officer’s quarters and a powder magazine topped by a lookout deck (see laser scan video by AIST and the University of Southern Florida, above).

The site’s history goes back to the 1500s when the Spanish were wrestling with the French to claim a section of the new continent’s southeast coast. Spain set up camp in what is now St. Augustine, Fla., and France had Fort Carolina up the coast to the north, near the mouth of the St. John’s River.

So, on to the massacre.

In September 1565, the French sailed to attack the Spaniards at Augustine, but a hurricane blew them too far south. They overshot their destination and wrecked somewhere around what would become Cape Canaveral. At the same time, a Spanish force headed north of Fort Carolina and, in the absence of a defending army, easily took the place.

Meanwhile, the shipwrecked French started hoofing it back up the coast toward their base. They had three problems. First, their path would have to pass the Spanish at St. Augustine. Second, Spain had already raided Carolina, so there wasn’t much to return to. But they never got to the point of figuring out the first to problems because (problem No. 3) the Spanish came down to meet them at an inlet 14 miles before they got to Augustine.

Outgunned, the French surrendered, but the Spanish also demanded they convert to Catholicism and massacred 111 Frenchmen who refused to give up their Huguenot faith. No one expects the Spanish Inquisition, especially not so far from Spain. The scene was repeated two weeks later when a group of French stragglers showed up at the same inlet, resulting in 134 dead.

People started calling the inlet Matanzas, a Spanish variation of massacre, and the name stuck.

A few years later, the Spanish built a wooden watchtower and thatched hut at the inlet, which provided an inland route for ships to approach Augustine. It was manned by six soldiers, whose main duty was to book it upstream and alert the Spanish base when they spotted enemies approaching. They thwarted attacks from pirates and were briefly captured by English outlaws.

The Spanish began worrying less about the French and more about the British, who were setting up forts in Georgia and Charleston, S.C. Spain began building up Augustine, breaking ground on what would be Fort Castillo in 1672. The wooden Matanzas outpost was converted to stone in 1740 and helped drive off the Brits on at least one occasion.

Not long after that, Spain traded Florida to the Brits in exchange for Cuba, which England had captured earlier. Then, Spain got Florida back in 1783 but turned it over to the United States in 1821. Included in the deal was Fort Matanzas, which by that time was a dilapidated property. The U.S. Department of War restored it, and it was later turned over to the National Park Service.