In 1917, the New York State board of Regents called on boys between the ages of 16 and 18 to receive physical and military training in schools.  In October of 1917, Trinity students began drilling exercises at the 71st Regiment armory.  The “Trinity Unit” as it was called, trained under Lieutenant Stecker every Friday after school.

This Acta Diurna piece indicates that the boys were greeted by Mr. Killefer and Mr. Bonsall at the 71st Regiment Armory and reports that William Brooks was appointed "Trinity Unit Line Sergeant."