The 4th Combat Engineer Battalion (USMC) is a military unit within the United States Marine Corps responsible for conducting various combat engineer operations. These tasks include breaching obstacles, constructing defensive positions, and performing mine clearance duties to ensure safe passage for troops during military operations. The battalion operates as part of larger Marine Expeditionary Units (MEU) or Marine Expeditionary Forces (MEF), providing engineering support in a wide range of environments. The 4th Combat Engineer Battalion, with its headquarters at Camp Pendleton, California, is one of the six active-duty combat engineer battalions in the USMC.