When Lt. Gen. Holland M. "Howlin' Mad" Smith and his V Amphibious Corps were preparing for the invasion of the Marianas -- Guam, Tinian, and Saipan -- they were expecting an easy fight. The Japanese appeared to be on the run. As D day for Saipan, the first of the three islands scheduled for conquest, loomed, V Corps operational planners felt safe in allocating a single division to serve as reserve for all three invasions.
The initial landings of the 2d and 4th Marine Divisions ran into fierce opposition, however, forcing General Smith to commit the army's 27th Infantry Division (the entire corps's reserve starting) that first night. Among the soldiers landing on Saipan was Lt. Col. William O'Brien. The exploits of O'Brien and his battalion were amazing, including the award of the Medal of Honor to battalion commander O'Brien.