The nuclear-powered submarine USS Michigan approaches to join the U.S. aircraft carrier USS Carl Vinson in drills near the Korean Peninsula, at Busan port in Busan, South Korea, Tuesday, April 25, 2017. North Korea marks the founding anniversary of its military on Tuesday, and South Korea and its allies are bracing for the possibility that it could conduct another nuclear test or launch an intercontinental ballistic missile for the first time. (Jo Jung-ho/Yonhap via AP)