More than 2,500 NATO troops are taking part in exercises on two training grounds in Lithuania.
Nine countries have sent soldiers to train as part of Exercise Iron Sword, Czech Republic, Estonia, the U.S., U.K., Canada, Lithuania, Luxembourg, Hungary and Germany.
Originally the exercise was to have involved only Lithuanian troops but was expanded in response to the Russian actions in Ukraine.
U.S. officer Lieutenant Bryan Blair said the aim of the exercise was to be able to communicate and fight together as one unit.
About 2,000 Lithuanian troops and 500 from the other NATO countries were using more than 300 combat vehicles in the two-week exercise.