The main Japanese force in the campaign was provided by the XVIII Army under the command of Lieutenant General Hatazō Adachi and was headquartered at Madang. This force consisted of three divisions – the 20th, the 41st and the 51st – and a number of smaller forces which included naval infantry and garrison units. Around the Finschhafen area in mid-September 1943, the main forces were drawn from the 20th Division's 80th Infantry and 26th Field Artillery Regiments, the 41st Division's 238th Infantry Regiment, the naval 85th Garrison Unit and a company from the 51st Division's 102nd Infantry Regiment. These forces were under the command of Major General Eizo Yamada, commander of the 1st Shipping Group, although tactical command was devolved at local level due to the geographical spread of the Japanese units. These units were situated across a broad area between the Mongi River, east of Lae to Arndt Point, Sattelberg, Joangeng, Logaweng, Finschhafen, Sisi and on Tami Island. The largest concentrations were around Sattelberg and Finschhafen, where the main forces came under the command of Lieutenant General Shigeru Katagiri, commander of the 20th Division. The strength and efficiency of the Japanese units had been reduced by disease, and their employment in road construction tasks between Madang and Bogadjim.