The pirates left their prisoners at the presidio, and these unfortunates were able to explain the daring raid. It went back to the argument Governor Guerra had had with the presidio’s French surgeon some time before. That disgruntled doctor was captured on his way to Havana by the pirates, who had already seized the supply ship from Vera Cruz. Seeing a chance for revenge on Guerra, the Frenchman conferred with his captors, apparently suggested the raid, and gave them the information they needed to work out a plan. Nor was this the only news from the prisoners. The invaders were the English. Furthermore, they had carefully sounded the bar, taken its latitude, and noted the landmarks with the avowed intent of returning in force to seize the fort and make it a base for their raids on commerce in the Bahama Channel. The fact that they did not leave the town in ashes lent credence to this report. In Spanish eyes, the 1668 sack of San Agustín (St. Augustine) was far more than a daring pirate raid on a tiny colonial outpost. St. Augustine was the keystone in the defenses of Florida. And Florida was highly important to Spain, not as a land rich in natural resources, but as a way station on a great commercial route. Each year, galleons bearing the proud banners of Spain drove slowly past the coral keys and surf-pounded beaches of Florida, following the Gulf Stream on their way to Cádiz. In these galleons were millions of ducats worth of gold and silver from the mines of Peru and Mexico. It was the year after Magellan’s ships encircled the world that the Conquistador Cortés dispatched a shipload of treasure from conquered Mexico. The loot never reached the Spanish court, for a French corsair took it to Francis I. That incident opened a new age in the profitable profession of piracy. Daring pirates of all nationalities sailed for the shelter of the West Indies. Florida’s position at the wayside of the life line connecting Spain with her colonies meant that this semitropical peninsula was of great strategic importance. Like the dog in the manger, Spain had to occupy the territory to prevent her enemies from using the marshy estuaries and natural harbors as ports from which to spread their sails against the commerce of her far-flung empire; and this same inhospitable country had to be made a refuge for the hundreds of mariners shipwrecked along the Florida reefs and the lee shores of the narrow channel. [Illustration: WHY SPAIN BUILT THE FORT] 1. Treasure ships sailed the Gulf Stream. Spain needed Florida to protect this life line 2. Enemy settlement came closer and closer to Florida 3. A strong fort would stop this English advance