Following the capture of Saipan, the 4th Marine Division was ordered to take part in the landing on near Tinian on July 24. The 1st Battalion was the first artillery unit ashore and immediately commenced a barrage of gunfire. During the morning of the following day, Japanese artillery hit the command post of the 1st Battalion and almost wiped out the unit's command structure, including its commander, Lieutenant Colonel Harry J. Zimmer.