During the Second World War the unit expanded as all students of military age who had been granted deferment were required to enroll as part of a National Service obligation. At its peak the unit was some 491 strong with 4 Infantry Companies, 2 Medical Companies and a Signals Section. Throughout the war the unit in conjunction with the University ran special technical courses for Royal Artillery cadets of which a total of 427 attended. In February 1943 the unit provided the backbone of the 9th City of Aberdeen (University Home Guard) Battalion, in addition to its normal role.