On the right flank , the 58th / 59th Infantry Battalion carried out a wide flanking move along a track that had been carved out of the west bank of the Hongorai by bulldozer . Beginning their move two days earlier , a number of patrols had had contacts with the Japanese . Meanwhile , using tractors to drag the tanks through the mud , the Australian armour had crossed the river also and by 16 : 00 on 20 May the battalion had managed to establish itself in an assembly area to the east of the river , unbeknown to the Japanese . The following day , the battalion left the line of departure and began to advance on its primary objective , which it reached in the early afternoon despite being held up while the tanks attempted to affect a creek crossing , and further delayed by stiff resistance . Later , after one of the battalion 's patrols came under heavy fire , the tanks moved up and attacked a Japanese gun position which the defenders quickly abandoned , leaving behind a 70 mm gun and a large amount of ammunition .