On 17 October 1966 during Operation Queanbeyan in Phuoc Tuy Province South Vietnam, Battalion Headquarters of 5th Battalion Royal Australian Regiment was held up by Viet Cong in a natural ambush position on a steep mountain track. 'The Anti-Tank Platoon commanded by Second Lieutenant Deak was directed to clear the area. The enemy were located in natural fire positions on both sides of a deep re-entrant with a gradient of one in two. One section of the platoon, covered by the remainder, swept up the re-entrant but the Section Commander was mortally wounded and the remainder pinned down by fire.
Second Lieutenant Deak redeployed the remainder of his platoon and under fire directed additional covering fire onto the objective from another Company 800 metres away. He then successfully directed the fire of armed helicopters onto the enemy positions and then led his platoon back into the re-entrant and cleared the enemy position without loss.
At all times during the three and one quarter hours engagement, Second Lieutenant Deak showed complete disregard for his own safety even when it became apparent that the enemy were concentrating their fire on leaders. The calm and competent manner of Second lieutenant Deak was a major factor in steadying his platoon under fire in a difficult situation. The success in clearing the Viet Cong ambush position was due in the main to the fine example of leadership and courage set by Second Lieutenant Deak.