 Davidson was promoted to major and assigned as Plans and Training Officer of the 2nd Battalion, 23rd Marines, and participated in the training phase prior to and during initial combat operations at the Battle of Saipan in the Marianas Islands (June 15 – July, 1944).On the fifth day of Saipan operations, Davidson was appointed battalion executive officer for the remainder of the Saipan battle and served in this capacity during the Battle of Tinian (July 24 – August 1, 1944).In October 1944, at the age of 25 and as a major, Davidson assumed permanent command of 2nd Battalion, 23rd Marines.