Marines from 3rd Battalion, 25th Marine Regiment, listen to a class on proficiency and conduct marks during a period of down time at Camp Grayling, Mich., at Exercise Northern Strike, Aug. 5, 2018. Exercise Northern Strike is a National Guard Bureau-sponsored training exercise that unites service members from multiple branches, states and coalition countries to conduct combined ground and air combat operations. (U.S. Marine Corps photo by Cpl. Niles Lee)