Reserve Marines with 4th Assault Amphibian Battalion, 4th Marine Division, dismount their Assault Amphibious Vehicles to attend a safety brief before participating in an obstacle clearing detachment practical application during Integrated Training Exercise 4-18, aboard Marine Corps Air Ground Combat Center Twentynine Palms, California, June 12, 2018. The OCD training was conducted to prepare Marines for the execution of a live-fire combined arms breach in which mechanized units will detonate a 1,000 pound mine clearing charge.