Sergeant Duncan was in command of a light armoured vehicle (LAV) which was part of a separate three-vehicle patrol positioned to the south of the vehicles which had come under attack.
As the battle with the insurgent forces intensified and KIWI Company sustained a number of casualties, the three patrol vehicles moved north to assist.
Approaching the contact site, the lead vehicle of Sergeant Duncan's patrol came under heavy fire from high ground to the north-east and west of their position.
As the lead vehicle came to a halt, Sergeant Duncan noticed a New Zealand soldier lying on the road in front of it exposed to insurgent fire.
Unable to get past the lead vehicle due to the narrow road, he manoeuvred his LAV behind it approximately 20 metres from the casualty. He dismounted his vehicle and ran into open ground.
After reaching the casualty, who had sustained a serious gunshot wound to the lower abdomen, Sergeant Duncan dragged him back until he reached the rear of the lead patrol vehicle, where he handed the casualty over to the company's nursing officer for treatment.
Sergeant Duncan then received a gunshot wound to his right leg as he returned to his own vehicle. Two soldiers, Lance Corporals Rory Malone and Pralli Durrer, died.
Sergeant Duncan's citation says, "His actions were in the finest tradition of the New Zealand Army."