A soldier is seen inthe command center of TRIDENT JOUST 15 military exercise in Cincu shooting range, 270km north of Bucharest June 25, 2015. The United States will pre-position tanks, artillery and other military equipment in eastern and central Europe, U.S. Defense Secretary Ashton Carter said on Tuesday, moving to reassure NATO allies unnerved by Russian involvement in Ukraine. Carter said the Baltic states - Estonia, Lithuania, Latvia -- as well as Bulgaria, Romania and Poland had agreed to host the arms and heavy equipment.