The 1st Medical Battalion was activated as part of the 1st Infantry Division in October 1940. They trained with the Division and arrived in the Mediterranean Theater of Operations in 1942. The battalion supported the division through all eight campaigns, from 1942 through 1945.

The standard here is styled after the U.S. Army Medical Department Regimental Standard with a maroon background and eagle. To differentiate it from others, the 1st Medical Battalion replaced the coat of arms with their own coat of arms symbols, the Bear of California, the Cross of Malta, and the armored arm. The ribbon reads, “IN OMNIA PROMPTUS” which means “prepared for all things”.

Medical Battalions were created to medically support Infantry Divisions. The battalion oversaw the evacuation of all casualties from the infantry battalion and regimental aid station. The collecting companies would also remove casualties directly from the field. Generally, a medical battalion had 34 officers, 470 enlisted men, and one chaplain.