Marines with 2nd and 4th Combat Engineer Battalions and 8th Engineer Support Bn. stand by during a breaching explosion aboard Marine Corps Base Camp Lejeune, July 24, 2013. Marines, all participants of the Sapper Leaders Course, spent one day executing urban demolition in order to learn advanced tactics, techniques and procedures in the combat engineer military occupational specialty. The course was the first of its kind, allowing Reserve Marines to participate with active-duty Marines to receive advanced training in the combat engineer MOS.