On 22 January, the Japanese fleet was sighted moving south by an American PBY flying boat, and on 23 January formations of Dutch bombers attacked the convoy. Despite this, the Japanese unit successfully landed approximately southeast of Balikpapan airfield on the evening of 24 January. The assault unit landed without meeting enemy resistance and, by dawn, had occupied the airfield. The southward advance moved slowly as the bridges had been destroyed, and the unit reached the northern outskirts of Balikpapan City on the night of 25 January. The Dutch garrison troops had been withdrawn and the Japanese entered the city without a fight.