Operation Reckless, the invasion of Hollandia and Aitape of 22-27 April 1944, was one of the most dramatic leapfrogging operations during the New Guinea campaign, and saw American forces bypass the strong Japanese bases at Wewak and Hansa Bay and capture key bases for MacArthur's planned return to the Philippines.
The first stage of the Allied offensive in New Guinea had been part of a wider plan to isolate the Japanese base at Rabaul. These attacks were carried out under the overall name Operation Cartwheel, which implemented the Elkton III Plan. On New Guinea Cartwheel had three phases - Operation Chronicle the invasion of Woodlark and Kiriwina Islands (30 June 1943), Operation Postern - which included attacks on Salamaua and Lae, the Huon Peninsula and Finisterre Range (lasting from June 1943 to April 1944) and Operation Dexterity, the invasion of the western end of New Britain (December 1943-April 1944). The web of Allied bases around Rabaul was completed by the by conquest of Los Negros and Manus in the Admiralty Islands (29 February-25 March 1944) and the occupation of Emirau on 20 March.
Once Rabaul was neutralised the next Allied objectives were the Japanese bases on the north coast of New Guinea. At the start of 1944 the key bases were Madang, the last target of Operation Postern, then west along the coast came Hansa Bay, Wewak, Aitape, Hollandia and Wakde. MacArthur's main aim was always the return to the Philippines. Hollandia was considered to be the most important position for this, and was the point from where the Allies could turn north to reach the southern Philippines. This was mainly because of the nearby Humboldt Bay, the best harbour on the north coast of New Guinea.
The original Allied plan had been to attack each of the north coast bases in turn, starting with Hansa Bay, and this was where General Adachi, the commander of the Japanese 18th Army, had concentrated most of his men. Early in 1944, while his troops were still fighting on the Huon Peninsula, in the Finisterre Range, on New Britain and on the Admiralty Islands, MacArthur decided to leapfrog Hansa Bay and Wewak, and head straight for Aitape and Hollandia. Allied air and American naval forces now effectively controlled the seas north of New Guinea, so the Japanese forces at Wewak would have to march across the incredibly difficult New Guinea landscape to intervene.
This was the most ambitious amphibious assault of the Pacific War to date. It would involve moving 80,000 men to a point 425 miles behind Japanese lines, making it the largest and longest range attack yet attempted. The nearest major Allied airbase was at Gusap, back in the Markham-Ramu area near the Huon Peninsula.
On 12 March the Joint Chiefs of Staff approved the new plan. D-Day for the new attack was set for 22 April. The Joint Chiefs also ordered Admiral Nimitz to use his fast carriers to support the attack on Hollandia. Nimitz and MacArthur met in Brisbane in late March, and agreed a detailed plan for the use of the carriers. Nimitz was worried about the reported 200 to 300 Japanese aircraft in the area, and insisted that his fast carriers would leave on D+2 (24 April), but did agree to provide eight escort carriers for eight days. In the meantime General Kenney's Fifth Air Force was to carry out a series of attacks on the Hollandia and Aitape areas. The Fifth would then provide B-25 and A-20 medium bombers to support the actual invasion. These pre-invasion raids devastated Japanese air power at Hollandia. Between 30 March and 3 April the Allies destroyed over 300 aircraft at Hollandia, and by 6 April the Japanese only had 25 serviceable aircraft at what had been a major air base.
A great deal of effort went into convincing the Japanese that Wewak and Hansa Bay were indeed the next American target. Kenney's aircraft bombed those areas just as much as Hollandia and Aitape. Naval forces bombarded the Wewak and Hansa Bay areas, and efforts were made to convince the Japanese that scouting forces were going ashore. At the same time Kenney's men carried out six raids on Aitape and Hollandia between 30 March and 16 April, destroying 351 Japanese aircraft. By the time the carriers arrived off Hollandia there was no real threat from Japanese aircraft.
Hollandia was the more important target. The Japanese had around 11,000 men in the area, although few of them were infantry. They also had three airfields some miles inland. Hollandia was also a potentially valuable naval base, with the best anchorage on the north coast of New Guinea. Aitape was more lightly defended, with about 1,000 men and two airfields. Aitape was attacked in order to allow the development of a forward Allied airbase within Australian New Guinea.
The deception efforts continued as the invasion fleet sailed west. After passing through the Vitiaz Strait the fleet moved north-west to the massive Seeadler Harbour in the Admiralty Islands. A total of 217 ships were involved, carrying 50,000 front line soldiers and 30,000 support staff. This made Operation Reckless the largest amphibious invasion of the Pacific War to date. The Japanese were entirely fooled, and as late as 21 April believed that Hollandia was very unlikely to be the next American target.
The 163rd Regimental Combat Team of the 41st Division landed at Aitape on the morning of 22 April. The Japanese were caught entirely by surprise and put up very little resistance. The airfield was secured within twenty four hours and the fighting was effectively over by 24 April. The Americans lost 19 dead during the short battle, the Japanese around 525. The Americans then pushed east to watch for any troops coming from Wewak.
Hollandia was attacked by the rest of the 41st Division and all of the 24th Division. The 41st landed at Humboldt Bay, where Hollandia town was located and the 24th further west at Tanahmerah Bay. Their target was Lake Sentani, inland from the coast and half way between the two bays. Despite problems with the terrain at Tanahmerah Bay both divisions made unexpectedly rapid progress. The 24th captured Hollandia Drome, the western of three airfields, on 26 April. The eastern force reached the lake on 24 April and then used LVTs to support their advance along the lake. Cyclops and Sentani Dromes were both captured on the 26 April and late on the day the two forces met up.
Just as at Aitape the Japanese had put up very little resistance at Hollandia. They did have impressive defensive positions ready to use, and an ambitious plan, but the plan was shattered by the initial bombardment. The effective Japanese commander, General Inada of the 6th Air Division, quickly decided to give up the fight and ordered his men to retreat west towards Wakde.
The American success at Hollandia and Aitape meant that General Adachi's Eighteenth Army was now cut off at Wewak. He was ordered to move west and push the Americans back into the sea, but soon realised that he wasn't strong enough to achieve this. Instead he decided to concentrate on an attempt to wipe out the Aitape beachhead. During May and early June the Americans encountered signs of the upcoming Japanese offensive, and were able to prepare for it. By the time the attack began the Americans were defending the Driniumor River, using the 2nd and 3rd Battalions, 128th Infantry and the 112th Cavalry. Although the Americans were ready for an attack, they didn't expect it to be supported by artillery. When the Japanese attacked on the night of 10-11 July they were able to punch a hole in the American lines and get a foothold on the western bank of the river. General Martin launched one counterattack, which failed, and then retreated west to a pre-planned delaying position three miles to the west. His decision wasn't supported further up the command chain and he was ordered to counterattack. Before this was done General Gill, commander of the 32nd Division, took command on the Driniumor front. The counterattack began on 13 July and the Japanese were soon forced back across the river. The Japanese had been unable to take advantage of their original success. They didn’t launch a second attack until the end of July, and although they had some local successes at the southern end of the line they never threatened the American position. On 31 July the Americans began a major offensive of their own. They were able to get behind the Japanese at the southern end of the line and on 9 August Adachi finally gave up and ordered a retreat back to Wewak. The Americans followed up for a short time, but then paused, and let the Japanese slip away to their remaining bases.
This remained the situation until the Australian 6th Division replaced the Americans at Aitape in September 1944. The Australians had been left behind by the advancing Americans and given the task of containing the isolated Japanese garrisons on New Guinea, New Britain and Bougainville. For largely political reasons the Australians decided to attack these isolated Japanese positions. At Wewak a lack of shipping meant that they were forced to conduct a land-based campaign, pushing east on two fronts, one near the coast and one on the inland mountains. The offensive began in mid-December 1944 and continued to the end of the war. The Japanese were eventually forced away from Wewak, but were still fighting when the war ended. This offensive cost the Australians 442 dead and 1,141 wounded, and was controversial within the division, where many felt that it had been a waste of lives. General Adachi surrendered with 13,500 men from his original 100,000.