Dirk Deverill, the foreign policy adviser to Air Force Global Strike Command, spoke on nuclear deterrence and the geopolitical environment at a Striker Speaking Series symposium at Ellsworth Air Force Base, S.D., July 21, 2016. Deverill discussed the relationships the U.S. has concerning China, North and South Korea, Russia and Daesh. (U.S. Air Force photo by Airman 1st Class Sadie Colbert)