 For the 1913 fiscal year , the General Board of the United States Navy determined that six destroyers would be authorized . The design for Destroyers No. 51 through No. 56 — what became the O 'Brien class , was to closely follow the design of the Cassin and Aylwin classes from fiscal year 1912 . The chief of the U.S. Navy 's Bureau of Ordnance ( <unk> ) suggested that the new destroyers be equipped with ten torpedo tubes and urged that the new 21 @-@ inch ( 533 mm ) torpedo be adopted . The General Board agreed in principle , adopting the 21 @-@ inch torpedo tubes , but eliminated <unk> 's proposed centerline torpedo tubes and keeping the number of tubes at eight , the same as the Cassin and Aylwin classes . The additional weight of the larger torpedoes , 5 long tons ( 5 @.@ 1 t ) of top weight , was offset by reducing the planned two aft @-@ facing guns to a single one . This gave the class four 4 @-@ inch ( 102 mm ) guns , which , again , matched the battery of the Cassin and Aylwin classes . The design for the O 'Brien class was approved on 20 August 1912 , and authorized by Congress on 4 March 1913 . 
