Situated in the town of Redzikowo near the Baltic coast, the base has been in the works since the 2000s and Warsaw says it shows Poland's military alliance with Washington remains solid, whoever is in the White House.
Polish President Andrzej Duda, a conservative who has stressed his warm ties with Trump, attended a function to open the base, which the Kremlin calls a bid to contain Russia by moving American military infrastructure nearer its borders.
Duda said: “This American base will be built on our land, in Poland... and from the moment this base is built here, the whole world will see clearly and distinctly that this is no longer a Russian sphere of influence.”
Trump's past criticism has unnerved some NATO members, as he vowed that the United States under his leadership would not defend countries that do not spend enough on defense.
However, Poland says it should have nothing to fear, as the alliance's biggest spender on defense relative to the size of its economy.
Missile shield
The U.S. base at Redzikowo is part of a broader NATO missile shield, dubbed "Aegis Ashore", which the alliance says can intercept short- to intermediate-range ballistic missiles.
Other key shield elements include a second site in Romania, U.S. navy destroyers based in the Spanish port of Rota and an early-warning radar in Turkey's town of Kurecik.
Moscow had already labelled the base a threat as far back as 2007, when it was still being planned.
NATO says the shield is purely defensive.
Military sources told Reuters the system in Poland can now only be used against missiles fired from the Middle East and the radar would need a change in direction to intercept projectiles from Russia, a complex procedure entailing a change of policy.
Poland’s defense minister, Władysław Kosiniak-Kamysz, said that with the opening of the missile base, his country “is becoming part of the best and most effective air defense system.”
