 To defend the naval base , heavy 15 @-@ inch naval guns ( 381 @.@ 0 mm ) were stationed at Johore battery , Changi , and at Buona Vista to deal with battleships . Medium BL 9 @.@ 2 inch guns ( 233 @.@ 7 mm ) were provided for dealing with smaller attackers . Batteries of smaller calibre anti @-@ aircraft guns and guns for dealing with raids were located at Fort Siloso , Fort Canning and Labrador . The five 15 @-@ inch guns were all surplus Navy guns , manufactured between 1903 and 1919 . Part of their cost was met from a gift of £ 500 @,@ 000 from Sultan Ibrahim of Johor for the Silver Jubilee of the coronation King George V. Three of the guns were given an all @-@ round ( 360 ° ) traverse and subterranean magazines . 
