[1] After a period of rest and reorganisation in Australia, the battalion returned to the Southwest Pacific theatre of operations in April 1945 when they were committed to the Borneo Campaign.

[2] The citation for his VC read:[3]Corporal Mackey was in charge of a section of the 2/3rd Australian Pioneer Battalion in the attack on the feature known as Helen, east of Tarakan town.

Led by Corporal Mackey the section moved along a narrow spur with scarcely width for more than one man when it came under fire from three well-sited positions near the top of a very steep, razor-backed ridge.

The ground fell away almost sheer on each side of the track making it almost impossible to move to a flank so Corporal Mackey led his men forward.

By his exceptional bravery and complete disregard for his own life, Corporal Mackey was largely responsible for the killing of seven Japanese and the elimination of two machine-gun posts, which enabled his platoon to gain its objective, from which the Company continued to engage the enemy.

His fearless action and outstanding courage were an inspiration to the whole battalion.The Japanese continued to hold off the attacking pioneers for a further two days before Helen was bombed with napalm, forcing them to abandon the position.