Within a century, Puerto Rico's position at the easternmost edge of what would become Spanish America helped it play a major part in the Spanish expansion toward Florida, the South American coast, and Mexico. It was usually the first port of call for Spanish ships arriving in the Americas; recognizing that the island was a strategic keystone, the Spanish decided to strengthen its defenses. By 1540, La Fortaleza, the first of three massive fortresses built in San Juan, was completed. By 1600, San Juan was completely enclosed by some of the most formidable ramparts in the Caribbean, whereas, ironically, the remainder of Puerto Rico was almost defenseless. In 1565 the king of Spain ordered the governor of Puerto Rico to provide men and materials to strengthen the city of St. Augustine, Florida.
By this time, the English (and to a lesser extent, the French) were seriously harassing Spanish shipping in the Caribbean and north Atlantic. At least part of the French and English aggression was in retaliation for the 1493 Papal Bull dividing the New World between Portugal and Spain -- an arrangement that eliminated all other nations from the spoils and colonization of the New World.
Queen Elizabeth I's most effective weapon against Spanish expansion in the Caribbean wasn't the Royal Navy; rather, it was buccaneers such as John Hawkins and Sir Francis Drake. Their victories included the destruction of St. Augustine in Florida, Cartagena in Colombia, and Santo Domingo in what is now the Dominican Republic, and the general harassment and pillaging of many Spanish ships and treasure convoys sailing from the New World to Europe with gold and silver from the Aztec and Inca empires. The Royal Navy did play an important role, however, for its 1588 defeat of the Spanish Armada marked the rise of the English as a major maritime power. The Spanish then began to aggressively fortify such islands as Puerto Rico.
In 1595, Drake and Hawkins persuaded Queen Elizabeth to embark on a bold and daring plan to invade and conquer Puerto Rico. An English general, the Earl of Cumberland, urged his men to bravery by "assuring your selves you have the maydenhead of Puerto Rico and so possesse the keyes of all the Indies." Confident that the island was "the very key of the West Indies which locketh and shutteth all the gold and silver in the continent of America and Brasilia," he brought into battle an English force of 4,500 soldiers and eventually captured La Fortaleza.
Although the occupation lasted a full 65 days, the English eventually abandoned Puerto Rico when their armies were decimated by tropical diseases and the local population, which began to engage in a kind of guerrilla warfare against the English. After pillaging and destroying much of the Puerto Rican countryside, the English left. Their short but abortive victory compelled the Spanish king, Philip III, to continue construction of the island's defenses. Despite these efforts, Puerto Rico retained a less-than-invincible aspect as Spanish soldiers in the forts often deserted or succumbed to tropical diseases.
