The CIB and EIB were established by Section I, War Department Circular 209, dated October 27, 1943:

The present war has demonstrated the importance of highly proficient, tough, hard and aggressive infantry, which can be obtained only by developing a high degree of individual all-around proficiency on the part of every infantryman. As a means of attaining the high standards desired and to foster esprit de corps in infantry units; the Expert Infantryman and the Combat Infantryman badges are established for infantry personnel.

This circular also stated that, "only one of these badges will be worn at one time" and that "the Combat Infantryman badge is the highest award."

Award of the CIB was officially authorized by an executive order dated November 15, 1943.

By Act of Congress approved on June 10, 1944, all soldiers, except officers, awarded the CIB were entitled to an additional $10 per month.

Army regulations issued during World War II never prescribed a specific period of time an Infantryman had to serve in combat to be eligible for the CIB.

In 1947, a policy was implemented that authorized the retroactive award of the Bronze Star Medal to soldiers who had received the Combat Infantryman Badge during World War II. The basis for doing this was that the CIB was awarded only to soldiers who had borne combat duties befitting the Bronze Star Medal and also that both awards required a recommendation by the commander and a citation in orders.

According to a personal memoir on the web, work to establish the CIB was initiated by General Marshall, who had been prompted by Medal of Honor recipient Major Charles W. Davis' observation to him that "it would be wonderful if someone could design a badge for every infantryman who faces the enemy every day and every night with so little recognition."