Poland on Thursday welcomed several thousand U.S. troops along with tanks and heavy equipment under a planned NATO operation to beef up its Eastern European allies, vexing the Kremlin, which said the troops’ presence is a threat to Russia.

The largest U.S.military reinforcement of Europe in decades of around 2,700 troops, out of 3,500 planned, arrived as part of operation Atlantic Resolve, aimed at showing Moscow Washington’s commitment to its allies.

“The main goal of our mission is deterrence and prevention of threats,” U.S. Army Colonel Christopher R. Norrie, commander of the 3rd Armoured Brigade Combat Team, said at a welcome ceremony in Poland’s western city of Zagan.

Poland and the Baltic former Soviet Republics requested U.S. and NATO troops after Russia’s annexation of Ukraine’s Crimea Peninsula in 2014, fearing further military operations in the region by President Vladimir Putin.

The Kremlin, which has previously criticized NATO for its reinforcement in Eastern Europe, said on Thursday the deployment was an aggressive step along its borders.

“We consider this a threat to us,” Dmitry Peskov, Kremlin’s spokesman, told journalists on a conference call. “We are talking here about a third country stepping up its military presence in Europe near our borders.”

Modernisation of the army has been a key priority for Poland’s year-old government run by the conservative Law and Justice (PiS) party, which built its popularity partly on promising greater security capabilities.

On Thursday, Polish Defence Minister Antoni Macierewicz said on the state TVP Info news channel that the NATO deployment puts an end to Russia’s influence in the region.

“Even after 1989 we had to continuously wonder whether the Russians won’t veto this or that action,” said Macierewicz, who has been seeking better ties and contracts with the U.S. military.

“Russia’s veto power in Central Europe, in Poland, has ended once and for all.”

Moscow, however, has already deployed in retaliation nuclear-capable Iskander missiles in its European exclave of Kaliningrad, in a move the U.S. State Department said was “destabilizing to European security.”

The U.S. deployment to NATO’s eastern flank includes more than 80 main battle tanks and hundreds of armored vehicles. The military unit will rotate through several countries, including Bulgaria, Estonia, Latvia, Lithuania and Romania.

“Their arrival is just one small but meaningful example of how we are quickly building combat power here,” Norrie said.