In order to create a suitable defense system at its perimeter, the Japanese navy decided to develop some of the atolls of the Marshall Islands into bases for seaplanes, for naval surface units submarines, and, with the advent of long-range land-based bombers, as airfields. Mili was only to become a small lookout, radio direction finding and weather station. After the begin of the war and the Japanese occupation of Kiribati, however, the strategic concepts changed. The development of Mili air base began in in autumn 1942 when the Korean and Marshallese labour force building the seaplane base on Majuro was transferred.
However, as the base was begun very late in the war, when Japanese resources were being stretched and when Japanese shipping was under attack by U.S. submarines, the base development is characterised by a relative absence of large concrete structures, such as command buildings, power stations or bunkers. In a very short time, between late 1942 and late 1943, the Japanese had constructed an airfield with three runways (4750', 4550' + 4400'), two hangars and a service apron. By end of 1943 there were also several hundred buildings, mainly of wooden construction, a wooden pier and several repair shops.
There was one radar set (range 50 miles) on island, giving the air wing some 10 minutes warning. During the war two squadrons of planes were temporarily stationed here many of which were destroyed on the ground. A large number of plane wrecks, mainly Zero-fighters (Mitsubishi A6M) and Betty-bombers (Mitsubishi G3M) are scattered about on the island.
The perimeter of the island, especially the ocean side, bristled with guns, which were a mixture of British and Japanese manufacture: 8 6" and 3 14cm coastal defense guns, 4 127mm dual purpose guns, 2 10cm mortars, 35 heavy and over 70 light anti-aircraft guns as well as an assortment of small guns.
Between mid-1943 and Aug. 1945, the US aircraft dropped 3350t bombs and US ships shot 450t shells onto Taroa. While the first attacks were carried-based and irregular, daily attacks were started after Majuro and Kwajalein had fallen to the US. At the same time, all supply lines to Mili were cut off, and the Japanese garrison was left to starve. Of the originally 5100 strong Japanese garrison (2600 Navy, 2500 Army,) only 2500 (50%) survived. Casualties occurred from air raids, diseases, accidents, and suicides, but mainly from starvation.