Russian planes fly very close to a U.S. destroyer in the Baltic Sea in 2016, sources say about 30 feet. The. U.S. protests the incident and this is discussed at a NATO-Russia Council meeting to avoid accidental flareup of tensions. Russia sees higher U.S. military presence near its borders as a threat. Russian response is to upgrade its nuclear submarine fleet and operate in the Baltic Sea, North Sea, Atlantic and Mediterranean. Russian intervention in Ukraine led to increased U.S. presence to protect the Baltic Republics and Poland, members of the NATO alliance. The U.S. and NATO is conducting Operation Atlantic Resolve to deter any Russian action. Chancellor Merkel called for a "persistent NATO presence in the Baltic States" during the Ukraine war in 2014, in a visit to Latvia. Germany led an early version of a Rapid Response Force of 5000 troops deployable in 48 hours setup in 2015.