Marines with Marine Wing Support Squadron 373 operate the Tactical Water Purification System—a capability used in humanitarian assistance and disaster relief missions—during exercise Pacific Horizon 2015 at Marine Corps Base Camp Pendleton, Calif., Oct. 23. PH 15 increases the ability of 1st Marine Expeditionary Brigade and Expeditionary Strike Group 3 to plan, communicate and conduct complex sea and shore based operations in response to natural disasters.