The U.S. is working to bolster Ukraine’s navy, a force that was decimated by Russia’s seizure of Crimea in 2014, an effort that comes as Moscow strengthens its own forces in the region in a buildup that some officials see as a threat to NATO’s southeastern flank. This is aimed to confront Russian threat in the Black and Azov seas.

The ramped-up effort to help Ukraine includes a military exercise that begun Monday called “Sea Breeze,” which is taking place days after Russia launched major military drills in the region involving nearly 150,000 troops, dueling shows of force that underscore the tensions between NATO and Moscow.

U.S. officials have long-accused Russia of building up its military forces in Crimea, stationing additional aircraft, warships, and missiles that can threaten countries in the region, making U.S. efforts to strengthen allies in the region more imperative.