Sentinel Solo Marine Corps Sgt. Darrin Smith operates a GAU-21/A from an aircraft during Sentinel Edge 19 at Cold Lake Air Weapons Range in Alberta, Canada, June 15, 2019. The exercise helps ensure combat effectiveness and proficiency. SHARE IMAGE: Download Image: Full Size (1.51 MB) Tags: training, exercise, Marine Corps Photo By: Marine Corps Lance Cpl. Jose Gonzalez VIRIN: 190615-M-EH454-087X.JPG Photo Gallery