Friday, August 12, 2011

Fort Étude – Fuerte San Diego, Acapulco Mexico

Why study forts? Forts where built in contested places of importance and epitomize the design principle “form should follow function”. I enjoy the forts at four levels of detail. First, there is the political level where we look to answer the question: “Who built this fort and why did they build it?” Second, there is the geographical level where we ask, “Why was the fort built at this site?” Third, looking at the geometric level answers the question, “Why was the fort built this way?” Fourth, at the detail level we ponder, “Why was this part of the fort built this way?”

Why This Location?

Acapulco was settled by the Spanish under Cortez in the 1530’s. Spanish explorer Magellan followed the trade winds West across the Pacific to the Philippines in 1521, but true trade could not begin until Andrés de Urdaneta discovered a return route North to the California coast and thence South to Acapulco in 1565. In Spain, Seville was given a monopoly on trade with the new world. What evolved was a trade route from Seville, to Havana, to Veracruz, to Acapulco, then on to Manila and back. Thus, Acapulco became the largest Spanish port on the West coast of the New World. After the defeat of the Spanish Armada in 1588, Spanish shipping was left vulnerable to English, French, and Dutch pirates. Something had to be done--convoys and forts were the two primary measures taken.

Spanish Trade Route

Why This Site?

Once the political decision was made to fortify Acapulco, the site had to be chosen. It was critical that the Manila Galleons anchored in the harbor and the warehouses for the Oriental goods awaiting overland trans shipments to Veracruz be protected from pirates. (Keep in mind that pirates like Drake and Morgan were “state supported terrorists” and might command as many as thirty ships with 1,200 troops!) Acapulco Bay is very large, but  the prime anchorage is in the small Northwestern corner. (Both the Acapulco Yacht Club and the cruise ship dock are in this corner of the bay.)

Range of Guns

 

Canon Ranges The most likely armament to be available had an effective range of about 1,200 yards—enough to sequester the anchored fleet. The actual site chosen was on a bluff which gave the guns an added advantage over shipboard armaments and made frontal assault extremely difficult. The fort was began in 1615 and extensively strengthen in 1776.
   

Why This Shape?

Fuerte San Diego is a classic bastioned star fort based upon a regular pentagon. The great military engineer Vauban proposed low forts with thick walls to withstand cannon fire that had obsoleted medieval forts with their high thin walls. He also perfected the star fort layout such that each  face of the fort could be swept by some of its own cannons.  Thus, there are no blind spots out of the reach of its guns.  The regularity of the fort suggests that the designers regarded a land based attack as an equal threat to sea side attack. In fact, the only time the fort fell it fell to a land attach during the revolution in the early 1800’s.

Diagram Acapulco 3 Fuerto San Diego 0

Generic Bastion Fort

Fuerte San Diego in Google

Why These Features?

As a tourist, I come upon a fort built and made obsolete long ago and affording no bird’s eye view. What is visible to the casual visitor are the myriad details. Each fort I visit has features and exhibits illuminating only slivers of the whole story. So as I describe the forts different aspects will be described many of which might have been present at previous forts, just inaccessible. 

Moats & Drawbridges

Most forts have a moat even if it’s just a dry ditch. There is usually one entrance to the fort and that is supplied with a drawbridge. These features were carried over from medieval fortification practices since their usefulness was not diminished by the advent of cannons.

Acapulco 3 Fuerto San Diego 3 Acapulco 3 Fuerto San Diego 1

Fuerte San Diego is Now a History Museum

A Low Wall Surrounds the Moat

Acapulco 3 Fuerto San Diego 10 Cruise Ship Acapulco 3 Fuerto San Diego & Covering Front Gate

The Bridge is Vulnerable to Flanking Fire

Bastion Embrasure for Flanking Gun

Embrasures

Embrasures are the low openings in the fort wall allowing the cannon to traverse an angle of fire while providing some protection for the gun crews. It’s the angle of travel (usually about thirty degrees left or right) that dictates the angles that the bastions can make with the main walls of the fort. Since Fuerte San Diego has cannons only on the parapet, it has only simple embrasures that are just low spots along the walls.

Museums

Many forts are currently being maintained as museums. Fuerte San Diego is now a fine history museum. It contains exhibits about the history of Acapulco and the Manila trade. Cruise ship passengers are the only contemporary invaders coming through in an endless series of tour groups. To a fort nut it is a little disappointing that there is not more interpretation of the actual military aspects of the fort.

 Acapulco 3 Fuerto San Diego 9 Tourists Invading Acapulco 3 Fuerto San Diego 14 Bridge to the Ships

Cruise Ships Dock Right Outside the Fort

New Bridge to Cruise Ship Dock

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