The US guided missile destroyer USS Donald Cook has left the Black Sea, two weeks after it was deployed there to reassure Eastern European allies worried by the Ukraine crisis, the Navy said Friday. (Photo by Alan J. Baribeau/U.S. Navy/Getty Images) ...

The US guided missile destroyer USS Donald Cook has left the Black Sea, two weeks after it was deployed there to reassure Eastern European allies worried by the Ukraine crisis, the Navy said Friday. (Photo by Alan J. Baribeau/U.S. Navy/Getty Images) ...

The US guided missile destroyer USS Donald Cook has left the Black Sea, two weeks after it was deployed there to reassure Eastern European allies worried by the Ukraine crisis, the Navy said Friday. (Photo by Alan J. Baribeau/U.S. Navy/Getty Images) ...

The US guided missile destroyer USS Donald Cook has left the Black Sea, two weeks after it was deployed there to reassure Eastern European allies worried by the Ukraine crisis, the Navy said Friday. (Photo by Alan J. Baribeau/U.S. Navy/Getty Images) ...

The US guided missile destroyer USS Donald Cook has left the Black Sea, two weeks after it was deployed there to reassure Eastern European allies worried by the Ukraine crisis, the Navy said Friday. (Photo by Alan J. Baribeau/U.S. Navy/Getty Images) ...

The US guided missile destroyer USS Donald Cook has left the Black Sea, two weeks after it was deployed there to reassure Eastern European allies worried by the Ukraine crisis, the Navy said Friday. (Photo by Alan J. Baribeau/U.S. Navy/Getty Images) ...