SWIDWIN, POLAND – APRIL 23: Members of the U.S. Army 173rd Airborne Brigade (R) and a Polish paratrooper unit attend a welcome ceremony upon the Americans’ arrival by plane at a Polish air force base on April 23, 2014 in Swidwin, Poland. Approximately 150 U.S. troops, as well as another 450 destined for the three Baltic states in coming days, will participate in bilateral military exercises over the coming weeks in a sign of commitment among NATO members. Tensions are rising in eastern Ukraine between Russian separatists and Ukrainian authorities and NATO is seeking to reassure its own members located close to Russia. (Photo by Sean Gallup/Getty Images)