Heavy transport losses had been incurred during the Balikpapan operation and it was felt that even heavier losses would be suffered if Bandjermasin was attacked from the sea, as it was closer to the Dutch air bases in Java and enemy bombers were active in the area. This, together with the fact that the Navy, being engaged in the invasion of Ambon and Makassar, was unable to provide sufficient escort, made it advisable to plan the attack, as much as possible, over land. Other deciding factors in the decision to attack over land was that the river mouth near Bandjermasin was too shallow, making it impossible to take transports up the river.
It was decided that Group Headquarters would not take part directly in the Bandjermasin operation, but instead would
remain in Balikpapan and assume operational command of the mopping up operations in the Sanga Sanga area and prepare for the invasion of Java.
The attack on Bandjermasin was to be carried out by two separate landing forces, Land Drive Unit and Sea Drive Unit.
The Land Drive Unit was supposed to leave Balikpapan on the evening of 30 January, land at Tanahgrogot before daybreak on the 31st and
immediately prepare to advance through the mountainous jungle terrain and than steadily south towards to Bandjermasin.
The Sea Drive Unit was to conduct an amphibious movement by landing craft, landing at a point approximately 80 kilometers southeast of Bandjermasin, where it should joined with the Main Force. The forces were to coordinate surprise attacks on Bandjermasin and capture the town. In order to keep the plan secret, sea transportation of troops was to be carried out only at night.
The only serious clash between the Imperial Japanese Army troops and colonial Dutch KNIL forces took place in the neighbourhood of the town of Moera Oeja which is about 40 km north of Tandjoeng. A small KNIL military outpost was stationed there because here the road led south to Bandjermasin, another important oil and port facility facing south towards the island stronghold of Java. The outpost consisted of only one KNIL brigade, which was given the task to observe Japanese troops movements, after which they had to link up with the forces at Tanahgrogot and together mount a fighting retreat. Shortly after the Japanese troops passed through gaps in the dense jungle mountains, they met with Dutch troops which were advancing north towards their objective and most probably on patrol around the foot hills of the jungle clad mountains as forward scouts. Apparently there were no casualties on either sides.
After this encounter, Japanese troops continued the march to victory southward, quickly occupying the towns of Moera Oeja, Bongkang, Tandjoeng, Amoentai, Barabai, Kandangan and Rantau, meeting no organised military resistance whatsoever. For the Dutch colonial territorial commander in Bandjermasin, Lieutenant Colonel H. T. Halkema, this was a very stressful and serious situation. He had only approximately 500 men under his command, of which about half of them were stationed at Kotawarangin airfield, near the city of Pangkalandoen, and he also had orders not to defend Bandjermasin, but to fight a protracted guerilla war.
The Sea Drive Unit under command of Captain Yoshibumi Okamoto left Balikpapan on the evening of 27 January 1942, three days ahead of the Land Drive Unit. The craft moved only at night and were carefully concealed in the river banks during the daylight hours and camouflaged with mangrove branches, while the troops were resting in the forest, so that they were completely hidden from aerial reconnaisance planes. Radio silence was maintained all the time. One naval officer was attached to the unit as a pilot. The surprise night attack was successfully carried out on the town of Kotabaroe on Laoet Island, as planned. Very little resistance was encountered and a large quantity of military supplies and provisions was captured.
Apparently the local administrative governor wasn't very pleased with his territorial commander and he asked the main Dutch Netherlands East Indies Army HQ on Java Island for a replacement. The replacement commander was on his way by airplane, but returned as they saw Bandjarmasin was on fire and they thought, although wrongly, that it was already occupied by Japanese troops and perhaps it would be unwise to attempt a landing. The Okamoto's unit landed at a point approximately 80 km southeast of Bandjarmasin on 8 February 1942 and advanced overland without opposition, to the airfield. As the Land Drive Unit had already dispersed the enemy, there was no fighting after the Sea Drive Unit reached the Martapoera airfield on 10 February 1942.
At 0900 on 10 February, the Martapoera airfield was captured by the Advance Force together with the Engineer Company. By the evening of the 10th February, with the arrival of the main force and the Sea Land Unit, Bandjermasin was finally occupied. There was no fighting.
Lieutenant Colonel H. T. Halkema came by sea to the Barito River, with his staff, accompanied by elements of units under his command. By now many KNIL native soldiers had already deserted with defeat of the colonial Dutch lingering in the air. Lieutenant Colonel Halkema received orders to proceed to Kotawarangin airfield. When he arrived there, with only 75 men left under his depleted command, he received an order to have part of his shrunken force, soldiers that were physically capable, to staunchly defend the airfield, while those remnants that are too weak and exhausted should to be sent to Java Island. Lieutenant Colonel Halkema was later even court-marshalled by the military court (Hoog Militair Gerechtshof). In the meantime a brave group of civilians, and military escapees, 180 persons, managed to evade the Japanese aboard a small coaster to Madoera Island, among which also included 20 women.
The official Japanese casualties during the Bandjermasin operation numbered only 9 soldiers who were killed or died from various
diseases, while at least 80% of the men were infected with malaria.
The casualties and the number of POWs on the Dutch side are unknown.
The distance travelled by land routes was approximately 400 km and the distance through jungle approximately 100 km.