After only a short period of respite, the 2/1st deployed to New Guinea, arriving there in September 1942 just as the tide of the Kokoda Track campaign began to turn back in the favour of the Allies. The battalion subsequently joined the Allied pursuit of the withdrawing Japanese north towards their beachheads around Buna–Gona, and during the counter-offensive the 2/1st Battalion were involved in the major battles at Eora Creek and then at Gorari, followed by Sanananda between October and late November 1942. Heavy casualties were suffered by the battalion during the campaign, with over 60 percent being killed, wounded or evacuated sick. Subsequent to the Kokoda campaign, the 2/1st returned to Australia to rebuild. At this time they received a large batch of reinforcements from the 49th Battalion, a Militia battalion that had fought around Sanananda before being disbanded.