The first of a 1,200-strong Nato force have arrived in Lithuania for deployment close to a key Russian exclave, amid growing security fears.
German officers have landed in the capital of Vilnius to coordinate the deployment.
More than 100 Belgian army troops and five dozen military vehicles also arrived in the port of Klaipeda, 37 miles from Russia's Kaliningrad exclave, which has a navy base and long-range missile systems.
Kaliningrad is squeezed between Lithuania and Poland.
The Belgians will join German, Dutch, and Norwegian troops at the Rukla base in central Lithuania.
At last year's Nato summit in Warsaw, the alliance decided to deploy forces in the countries bordering Russia and Belarus.
There is a fear in the Baltic countries and Poland, that after Russia displayed its might in Georgia and Ukraine, the former Soviet republics could be next.
Earlier this month, dozens of US Special Forces soldiers were deployed along Europe's eastern flank to reassure Latvia, Lithuania and Estonia.
Britain will send an 800-strong battalion to Estonia, supported by French and Danish troops, from May.
Elsewhere, Canada is sending 450 troops to Latvia.
In October, Russia deployed nuclear-capable Iskander missiles to its Kaliningrad exclave.
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