First Line of Defense

First Line of Defense , The walled city of San Juan had several levels of protection outside its wall that were known as lines of defense, defined by the firing range of the artillery. The first line of defense, so called because it was the first that enemies approaching by land would encounter, was the farthest from the walled city. It ran along the extreme eastern edge of the San Juan Islet, and compromised various defensive elements built at different times. Among these, the San Jerónimo Fort, the San Antonio Fortified Bridge, the San Jerónimo Magazine and its guardhouse all appear on a 1772 plan by Thomas O'Daly., From that time on, Thomas O'Daly and Juan Francisco Mestre, prominent engineers of the period, reinforced the first line and transformed it into a sophisticated defensive network created to hold off any enemy advance from the east. The system was reinforced and connected by parapets designed to facilitate troop movement while protecting soldiers from enemy artillery fire. These parapets roughly followed the contours of the Islet's then existing eastern shore, before the mangroves were filled in. The parapets ran from the small battery at Escambrón Point at the north to the mangroves of the San Antonio Channel at the south., Some elements of the first line remained in military use until the beginning of the 20th century, but from then on this important component of the Islet's defensive system was gradually mutilated. Construction of the city's first horse racetrack (now demolished) in the area of El Escambrón was the first development to negatively impact the system. Today, only a few scattered sections and pieces of the elaborate system remain., An early version of this fort was built in 1532, to protect the eastern coast of the San Juan Islet, which overlooks the protected cove known as El Boquerón. During the 17th and 18th centuries it was improved until it became the San Jerónimo Fort, which can be seen on the seashore, to the north. This fort and the fortified San Antonio Bridge were the key components of the first line of defense., In April 1797, a force of 3,910 English soldiers under the command of Sir Ralph Abercromby disembarked from 60 vessels anchored at Cangrejos Cove, to the east. The fort, commanded by Coronel Teodomiro del Toro, resisted the English bombardment and forced the retreat of the invaders. According to tradition, del Toro “rebuilt by night what the English destroyed by day.” The fort was severely damaged, but was rebuilt by 1799, and continued to serve as a military post until the early 20th century., From the 1960's to the 1980's it housed a military museum sponsored by the Institute of Puerto Rican Culture.,