This week, SU-24 fighter-bombers buzzed a U.S. destroyer in the Baltic Sea. The Russian planes carried no missiles or bombs.
Message: What are you Americans doing here?
In the South China Sea, U.S. planes overfly, and U.S. warships sail inside, the territorial limits of islets claimed by Beijing.
In South Korea, U.S. forces conduct annual military exercises as warnings to a North Korea that is testing nuclear warheads and long-range missiles that can reach the United States.