The Japanese 18th Army was subsequently ordered to withdraw to Wewak in late March; as the 51st Division withdrew to the Wewak area, the 20th Division held Hansa Bay, and the 41st Division carried out rearguard operations around Madang throughout April. Severely depleted, in all, the three divisions only fielded about 20,000 troops. In late 1944, US troops carried out a landing at Aitape and began operations to isolate the Japanese garrison there as part of the Western New Guinea campaign, later clashing around the Driniumor River. They were subsequently relieved in late 1944 by Australian troops from the 6th Division, which launched the Aitape–Wewak campaign, fighting to secure the airfield and then clear the Japanese from the inland areas, patrolling through the Torricelli and Prince Alexander mountain ranges until the end of the war in August 1945. Meanwhile, troops from the 8th Infantry Brigade remained in the Madang area until the end of the war.