The 403rd Infantry (PEACEMAKER) Brigade traces its roots to the 3rd Infantry Brigade of the 4th Infantry Division, otherwise known as the 3/4th Brigade, being the forerunner of the unit, when it was organized on 15 July 1973 pursuant to General Order Nr 41 Headquarters Philippine Army dated 3 July 1973.

Since then, it facilitates the command and control of the newly organized Infantry Battalions as called for by the ever growing Muslim secessionist movement in the 4ID AOR.

The Brigade was operationally organized and deployed on 15 September 1973 with its first headquarters at Pagadian City under its first Brigade Commander, Colonel Oscar Aleonar, who was also then the Assistant Division Commander of the 4th Infantry Division.

The 403rd Infantry (Peacemaker) Brigade conducts Internal Security Operations (ISO) in the assigned area of responsibility (AOR) of the 4th Infantry Division in Camiguin, Bukidnon and Misamis Oriental Provinces to dismantle and destroy the remaining guerilla fronts of the Local Communist Movement (LCM), hold and contain the Moro Islamic Liberation Front (MILF) in Wao and Bumbaran of Lanao del Sur and destroy other threat groups in order to attain peace and stability conducive to sustainable development in assisting the Philippine government in its socio-economic development projects; and assists the Philippine National Police curb criminalities in the area.

The following are the Infantry Battalion units that are presently placed under operational control of the brigade: