Poles have wanted US troops on their soil as a deterrent against Russian Federation.
Last week some 2,500 items of military equipment arrived in Germany and have since been moved in transports across the continent.
Eighty-seven battle tanks, 144 Bradley fighting vehicles, and over 3,000 soldiers are on their way from Germany to Poland.
After the military exercises, the soldiers are to be distributed among Poland, Bulgaria, Romania, and the Baltic countries.
A spokesman for Russian President Vladimir Putin called the deployment of USA troops in Poland a threat to Russia's security and interests.
London breaches annual air pollution limits in five days
This year's first breach in London was on the main A23 road running through Brixton in South London. While these are vital steps in the right direction, we can't wait another three years for action.
In the nearby town of Zagan - known for notorious POW camps the Nazis set up, including one featured in the 1963 blockbuster The Great Escape - officials and residents waving small American flags celebrated the arrival of what will be a continuous, rotational presence of USA and North Atlantic Treaty Organisation armored brigades in Eastern Europe. It was described as the "biggest" deployment of the U.S.in Europe since the Cold War. He added it's important to "be together, to build our common relationship and to provide more security" - not only for Europe, he said, but the world.
The operation comes a week before President-elect Donald Trump's inauguration, who has announced that his Republican administration will work to ease tensions with the Kremlin amid concern over accusations of Russian intervention in the 2016 USA elections. "That's a buildup of military presence and I have nothing to add", he concluded, after being asked whether the new United States deployment presented a real threat or was simply annoying to Russian Federation. The US also plans to send more troops to bases in the Black Sea, the Netherlands, Belgium and Germany, while the United Kingdom plans to send an 800-strong battalion to Estonia in May. "I don't know that I'm going to get along with Vladimir Putin".
Russian Federation has been highly critical of the deployment.
Polish Foreign Minister Witold Waszczykowski expressed hope this week that any new effort at reconciliation with Russian Federation "does not happen at our expense".