Fort Slocum ( New York ) Fort Slocum , New York was a US military post which occupied Davids ' Island in the western end of Long Island Sound in New Rochelle , New York from 1867 - 1965 . The fort was named for Major General Henry W . Slocum , a Union corps commander in the American Civil War . History . " Military " use of this island dates in fact to 1861 , when the 3rd Regiment of the Irish Brigade established its Camp Carrigan . The next year , 1862 , Davids ' Island was leased by the U . S . Government . This marked the first use of Davids ' Island by the " regular Army . " At that time , De Camp General Hospital was established to serve thousands of wounded individuals from the battlefields of the American Civil War . By late 1862 , De Camp was the Army ’ s largest general hospital , housing more than 2 , 100 patients . Originally , De Camp General Hospital treated only Union soldiers , but following the Battle of Gettysburg in July 1863 , the War Department opened it to care for hundreds of wounded Confederate soldiers . Even though a prison camp had been established on Hart Island in 1865 Davids ' Island soon held more than 2 , 500 Confederate prisoners of war . Most had recovered by October , and they were moved to prisoner - of - war camps elsewhere . A ferry connection was established from Neptune Island , under the control of Simeon Leland . At the end of the war , Congress authorized the island ' s purchase for military purposes and it was conveyed to the United States in 1867 . From this date , the Federal government had operated its own ferry to and from Neptune Island . In July 1878 Davids ’ Island was made a principal depot of the U . S . Army General Recruiting Service , taking over this assignment from Governors Island . This marked the beginning of the installation ’ s longstanding mission as a recruitment and training center . As the post on Davids ’ Island grew , the Army invested in new brick construction of more than 20 new buildings , including officers ’ quarters , enlisted men ’ s barracks , mess halls , hospital buildings , and support facilities . It was later converted to a coastal artillery defense post and was given the name Fort Slocum after Major General Henry W . Slocum , U . S . Volunteers . Construction of fortifications on the island resulted from the recommendations of the Endicott Board on Fortifications , an 1886 study of America ’ s coastal defenses . The study called for better protection of ports such as New York Harbor and Davids Island became part of its system of defenses . Between 1891 and 1904 , artillery batteries were erected at three places on the eastern half of the island — Battery Practice near the southeastern shoreline : Battery Practice , mounting among others the 15 " muzzle - loading smoothbore black - powder gun ( still on display at the island ) ; the state - of - the - art Abbot Quad heavy mortar batteries , Haskin and Overton , mounting a total of 16 breech - loading 12 " rifled guns , at the southeast end of the island ; and two adjoining medium - range breech - loading rifled gun batteries , Fraser and Kinney , on the northeastern shore . With improved naval gunnery at the beginning of the 20th century , these batteries became obsolete , and Ft . Slocum was removed in 1907 from the Artillery District of New York . ( Despite the presence of postcards , including those in the New Rochelle Public Library , there were never large - caliber breech - loading disappearing guns placed at Davids ' Island . ) At the start of the 20th Century the Davids ' Island had become the East Coast assembly point for units being assigned to America ’ s new overseas operations . By the onset of World War I it had become one of the busiest recruiting stations in the country , processing 100 , 000 soldiers per year and serving as the recruit examination station for soldiers from New York , New Jersey , Pennsylvania and the New England states . Between 1917 and 1919 , over 140 , 000 recruits passed through the post . In fact , Recruit Week in December 1917 brought so many recruits to Fort Slocum that an overflow had to be housed in New Rochelle . From 1946 to 1949 , Fort Slocum housed Headquarters First Air Force . It was renamed " Slocum Air Force Base " in June 1949 ; this only lasted for a year before being turned back into an Army post in June 1950 . From 1955 to 1960 , Fort Slocum housed Nike Ajax air - defense battery NY - 15 . The missiles were stored in underground silos on nearby Hart Island , with the radar and control base situated on Davids ' Island . In July 1960 , after only five years of operation , Nike Battery NY - 15 was closed . From 1951 to 1962 , Fort Slocum was the home of the U . S . Army Chaplain School . From 1951 to 1954 , Fort Slocum was home to the joint - services Armed Forces Information School From 1954 , this was truncated to the Army Information School ; from 1964 , this was again reorganized into the joint - services Defense Information School , which it still remains at its current home at Ft . Meade , MD . Over the course of this time , troops from the various services , officers and enlisted , male and female , American and allied , were trained in applied journalism ; oral communication ; radio / TV broadcasting ; public and world affairs ; and photography . In 1965 , the information school was moved to Fort Benjamin Harrison , Indiana when Fort Slocum was deactivated . Fort Slocum was deactivated on November 30 , 1965 . During the decades that followed , the facilities of the former Army post were neglected and deteriorated severely and continued to occupy Davids ’ Island into the beginning of the 21st century . The ruins were among the factors complicating redevelopment of the island . Beginning in 2004 , however , Congress appropriated funds to remove the ruins through a Defense Department program that assists communities in reusing former defense facilities . During the summer of 2008 , the city of New Rochelle demolished all remaining structures on the island , including the iconic water tower on the northern end of the island , with plans to turn the island into a park . " Sound off , one , two " . The famous " Sound off , one , two " military cadence was invented at Fort Slocum in 1944 . Other uses of the name . Fort Slocum was also the name of a Civil War fort defending Washington , D . C . , although it was named for a different Slocum ( Colonel John S . Slocum of Rhode Island , killed at the First Battle of Bull Run ) . The Library of Congress web site contains two photographs titled , " Officers , 4th U . S . Colored Infantry , Fort Slocum , April , 1865 " . Since that regiment was never stationed north of Baltimore , Maryland , it is likely that the Fort Slocum referred to was the one in Washington , D . C .