Lieutenant Colonel P. H. Oxley was the first Commanding Officer, but when he was promoted colonel in September 1965 command passed to Lieutenant Colonel J. A. Warr. This was a challenging time for the new unit. According to O'Neill: "The First Battalion was in the final stages of its preparations for departure to Vietnam, and so the Fifth came in for more than its usual share of routine chores and administrative duties. In order to foster high spirit in the new battalion, the idea of becoming known as the 'Tiger Battalion' was introduced and this spread rapidly and spontaneously amongst its members. From that time on Fifth Battalion were the Tiger Battalion, from the gold of their lanyards to the tiger tails tied onto the kitbags leaving for Vietnam in April 1966."