Artillery exhibit in the Joint Operations Command Center at Castillo San Cristóbal, San Juan National Historic Site

Castillo San Cristóbal Main Page

The Spanish-American War (April-December 1898), which came about when the United States became involved in the Cuban struggle for independence from Spain, ended in a Cuban / American victory. Per the terms of the Treaty of Paris, the United States took possession of Puerto Rico, the Philippines, and Guam. The U. S. military then decided to occupy all of them. Ironically, while the U. S. fought with the Filipino revolutionaries to overthrow Spain, it found itself in a war with the Philippines less than a year later once these same revolutionaries figured out that the U. S. was just another Spain. In Puerto Rico, there were pro-American and anti-American points of view, but the American presence promised to boost the economy, so the occupation was tolerated.

While Puerto Rico was an important base for the United States military in the early 1900s, the Spanish fortresses themselves had been rendered obsolete by advances in artillery made during the U. S. Civil War. Like all forts of the time, they were masonry forts. Stone and brick had no problem stopping a typical cannonball, for these didn’t travel with much velocity, nor were they very accurate, so the chance of blasting a hole in a fort wall by hitting the same spot over and over again was slim. However, rifled artillery developed during the mid-1800s had an inner barrel with a spiral grove cut into it. When fired, they sent bullet-shaped shells spinning like footballs, increasing not only their accuracy, but also their range and velocity. Blasting apart masonry forts was no longer a problem, and from that moment on, all forts in the world up to that point become obsolete for defensive purposes. And the coming of airplanes just made the forts even more ineffective. Spain tried to modernize the forts in preparation for the Spanish-American war by installing a few new artillery pieces, but this proved completely ineffective against the U. S. war ships.

The U. S. Army used the forts as headquarters and training facilities for operations in the area. At Castillo San Cristóbal, the Army installed a new sewer and plumbing system in 1899, electricity in 1901, and troop housing on the location of the Princess Battery in 1931, demolishing much of this historical structure. However, it did little to rearm the fort. In fact, at the end of World War I there were no guns at all installed at San Cristóbal. The war ships in the harbor were what deterred an enemy attack, as they had more firepower than any land-based artillery that the Army was willing to spend money on during peace time.

It wasn’t until World War II came around that major additions to the fort were made. Four 6.1-inch guns were installed on the grounds of San Cristóbal, and other large guns were placed at Castillo San Felipe del Morro and some of the islands at the mouth of San Juan Bay. Two fire control towers, which were used to spot enemy ships and help provide firing coordinates for artillery, were also built at San Cristóbal, one at the north end of the cavalier and one on the main terreplein.

The largest project was the 1942 addition of a bomb-proof building that was constructed in the dry moat between the fort wall and the San Carlos Ravelin. The roof was covered with grass so that from the air it looked like just another field. This building was the Joint Operations Command Center (JOC), the Army’s communications hub and the headquarters for the Antilles Air Command, which directed air and naval forces in the Caribbean from the Bahamas to Antigua.