The battle of Wau (28-30 January 1943) saw the defeat of the last Japanese attempt to advance towards Port Moresby
In March 1942 the Japanese occupied Lae and Salamaua, on the shores of the Huon Gulf, at the eastern end of the long coast of the Territory of New Guinea. In response the Australians moved two companies of commandoes to the small town of Wau. Wau is located in the upper reaches of the Bulola Valley. The river flows north-west from Wau and into the Markham River, which then flows east into the Huon Gulf. Wau also had a difficult but usable airfield, which made it a potentially valuable base for any Allied counterattack into the Markham Valley. From the Japanese point of view its main advantage was that it sat on a trail that ran from Salamaua on the north coast over to the south coast of Papua. Wau was only thirty miles south of Salamaua, although this route cut across a mountain range and was unknown to the Australians.
The airfield was 3,600 feet long and dropped by 300 feet (or 10%). As a result it could only be used in one direction, landing uphill and taking off downhill, regardless of the wind direction. It was also often covered with cloud and unusable.
In early January the Japanese managed to get 3,000 reinforcements under General Tooru Okabe to Lae. They then moved along the coast towards the village of Mubo, and then turned inland to head for Wau.
The Allies were aware of the threat to Wau, and prepared to airlift in the 17th Australian Brigade from Milne Bay. This movement began in mid-January but was hampered by poor weather, and stopped completely on 26 January.
The fighting began on 28 January. The Japanese ran into a small Australian force under Captain W. H. Sherlock at Wandumi, four miles from Wau. Their first attack, which came before dawn, was repulsed, but they returned later in the day. This time they bypassed the outnumbered Australians, and got to within 400 yards of the airfield, where they were stopped.
Early on 29 January the weather finally relented. A dramatic airlift began. The Australian reinforcements ran straight from their aircraft into battle, and helped repulse the Japanese attack. A total of fifty seven plane loads of reinforcements arrived on 28 January and more followed in the next few days. By the end of the first three days 194 plane loads had been delivered.
On 30 January General Okabe launched a major pre-dawn assault on the airstrip, but this was repulsed. After the failure of this attack the Japanese withdrew towards Salamaua.
The Japanese had to retreat back to Salamaua and Lae, ending their last significant offensive on New Guinea. The few major Japanese attacks later in the campaign would all be counterattacks, attempting to repel Allied advances.