The carriers arrived at Kure on 29 December. They were assigned to the Southern Force on 8 January 1942 and departed four days later for the Dutch East Indies. The ships supported the invasion of the Palau Islands and the Battle of Ambon, attacking Allied positions on the island on 23 January with 54 aircraft. Four days later the carriers detached 18 Zeros and 9 D3As to operate from land bases in support of Japanese operations in the Battle of Borneo. "Hiryū" and "Sōryū" arrived at Palau on 28 January and waited for the arrival of the carriers and "Akagi". All four carriers departed Palau on 15 February and launched air strikes against Darwin, Australia, four days later. "Hiryū" contributed 18 B5Ns, 18 D3As, and 9 Zeros to the attack. Her aircraft attacked the ships in port and its facilities, sinking or setting on fire three ships and damaging two others. The Zeros destroyed 1 P-40E as it was taking off, 2 Consolidated PBY Catalina seaplanes on the water, and a Zero was forced to crash land after being damaged by a P-40E of the United States Army Air Forces (USAAF) 33rd Pursuit Squadron.