The bulk of the 43rd division left Tateyama, Chiba on 14 May 1944 and reached Saipan uneventfully on 19 May 1944.

About 9000 troops and 13 artillery pieces of the 43rd division then dug in around Mount Tapochau, with the rest spread over the southern part of Saipan island.

Overall, the 43rd division managed to add one line of trenches to the pre-existing defences before the arrival of the US invasion fleet on 13 June 1944.

Although the division was able to re-capture the local high ground around Hinashita hill,[1] the Japanese gains were dramatically reversed in the morning of 18 June 1944, when the US forces captured Hinashita hill and an airfield in the south of the island largely intact.

On 27 June 1944, as the Mount Tapochau defences were failing rapidly, Yoshitsugu Saitō, the 43rd division commander, radioed Tokyo asking for either reinforcements or evacuation by air.