Fort Brooke , Puerto Rico Fort Brooke was a United States Army camp established on 3 March 1943 under General Order Number 10 during WWII after the German U - boat attacks of 1942 on the Caribbean Basin in conjunction to Operation Z . Early years . During the early years , Puerto Rico played a leading role as the operations center in the " Antilles Screen " against German U - boats , whose attacks reached an alarming peak in 1942 with the sinking of 336 ships in the Caribbean area . Ships sailing from " South American " ports carried such strategic products as gasoline , oil derivatives , and bauxite for aluminum production , and their losses were serious . Puerto Rico provided support for U . S . naval forces charged with controlling the Caribbean ; it served as a base for air protection for ships , other outposts in the region , and the approaches to the Panama Canal ; and it was an important link in the transport and ferrying route for aircraft , personnel , and cargo going to Africa and Middle East . On May 1942 , " U - boats " sunk 56 ships totaling more than 248 , 000 tons of shipment in the space of " 4 months " all throughout the Caribbean Sea Frontier west of the shipping control line . By the middle of the month , 22 % of the bauxite fleet had been destroyed , 20 % of the ships in the Puerto Rican run had been lost , and of 74 vessels allocated to the Army for the month of 17 July had already been sunk . Formation . Anxious at the beginning of World War II to avoid raising fears of the U . S . expansion in the hemisphere through the creation of military bases in Latin America , President Roosevelt concentrated instead on strengthening defenses at both ends of the U . S . Canal Zone , and establishing an air base and other military installations on the island of Puerto Rico , the major U . S . territory in the Caribbean Basin . In the President ' s opinion , expressed in a bill that failed to pass in the U . S . Senate in 1943 , the chain of islands running in a great arc from New Orleans to the shoulder of South America , enclosing the Caribbean Basin , formed a vast natural shield for the Panama Canal , suited in distance and conformation to the uses of the military plane . And of this island shield , Puerto Rico is the center . Order 10 . General Order No . 10 read : The Headland Castle at Old San Juan will be named Fort Brooke in memory of United States Army Major General John Rutter Brooke from Pennsylvania , better known as " John Ruller " during the American Civil War between 1861 and 1865 and the Spanish – American War of 1898 . Description . Fort Brooke was located in Fort San Felipe del Morro , a Spanish colonial fort . It consisted of offices for technicians , observers , military staff and police , music band members , motor pool workers and medical personnel . Officers ' quarters were constructed along the road leading to the Castle surrounded by an Officers ' Club , one swimming pool , the Bachelor Officers ' Quarters ( BOQ ) and one outdoor cinema on top of a golf course . Observation posts , communications centers and underground installations were also added in the sector . Due to declining maritime losses in the Atlantic as the war progressed , the base saw little action in the later war years , and became home to a number of sporting and leisure activities . Transformation into a hospital . On 31 August 1944 , the United States Department of War issued General Order No . 71 which transformed the Ballajá station into the Fort Brooke Hospital installation . Armed Forces Examination and Induction Station . Puertoricans drafted to the U . S . Military during the Korean War and the Vietnam War reported to the Armed Forces Examination and Induction Station ( AFEIS ) at Fort Brooke for screens and processes before being sent to active duty . In 1970 Armed Forces Examination and Induction Station at Fort Brooke was redesignated as the Armed Forces Examining and Entrance Station . In 1978 the station moved to a new facility in Guaynabo , Puerto Rico near the Fort Buchanan Army base and became the Military Entrance Processing Station ( MEPS ) .