Military vehicles and troops from Britain, France, Germany and the Netherlands are deploying to Poland and the Baltic states to support NATO's forward presence.
The move is part of the alliance's Readiness Action Plan, a strategy aimed at curbing Russian aggression in eastern Europe. 17 NATO allies plan to contribute to the effort, according to IHS Janes.
The U.K. Ministry of Defense announced the first 120 soldiers arrived in Estonia with armored vehicles including Challenger 2 tanks, Warrior infantry fighting vehicles and AS90 howitzers.
U.K. Defense Secretary Michael Fallon called the deployment one of his country's largest in the region since the fall of the Soviet Union.
"This is the start of one of the biggest deployment in Eastern Europe since the Cold War and by the end of next month, we will have 800 British troops, with armor, with tanks, ready to help reassure our allies and to underline our commitment to the security of Europe," Fallon said in a press release.
France plans to send 300 troops to support the British, while the Netherlands will deploy over 100 soldiers to Lithuania to support its German, Belgian and Norwegian allies stationed in the same area.
Germany will lead the largest effort, fronting 1,200 troops for the deterrence mission.