Over 1,000 pieces of USA equipment, including Abrams tanks, Bradley fighting vehicles and self-propelled howitzers, arrived at the port of Gdansk on Wednesday.
The arriving U.S. tanks are joining four multinational battalions recently deployed to Poland, Lithuania, Latvia and Estonia amid fears over Russian intentions throughout the region.
"Atlantic Resolve demonstrates the United States commitment to the security of NATO allies on air, land and at sea".
In the drills, which cover a vast area from Belarus and Russia's Western borders up into the Arctic, the two countries' troops will battle a fake state invented for the goal.
The exercises that Russian Federation is conducting with its Eastern European ally, Belarus, have attracted intense attention amid nervousness over Moscow's recent military adventures and its tensions with the West.
Colonel General Andrei Kartapolov, commander of Russia's Western Military District, said in an interview published by the Russian military's official Krasnaya Zvezda newspaper on September 13 that the number of troops and hardware used in the drills "will fully comply with the Vienna Document". Part of the drills took place on a patch of land in the Suwalki Gap, which borders the Russian exclave of Kaliningrad. "And I am sure that we will restore our relationship with NATO and we will return to the wonderful form of cooperation that is the Russia-NATO Council".
North Atlantic Treaty Organisation has also bolstered its presence in its easternmost member states that were dominated by Moscow during the Cold War and remain concerned about the Kremlin's intentions in the region.More news: Arsenal boss Wenger: No excuses for Chelsea after Thursday Euro tie
In a July statement, the Swedish Armed Forces wrote that "several other countries" had been invited to take part in the exercise to enhance "Sweden's defense capability against a larger, sophisticated opponent", in what appeared to be a reference to Russian Federation.
Michael Kofman with the Center for Naval Analyses said at the briefing that the joint exercises will not only show the nuts and bolts of Russia's troop placement, but also Russia's ability to intervene on Belarus' behalf if it is threatened.
Russian Federation and Belarus are set to launch their own Zapad war games on Thursday, which will involve up to 12,700 troops, 70 aircraft, and almost 700 land vehicles.
"Ukraine was attacked shortly after the Zapad 2013 exercises, and a few years earlier there was the attack on Georgia, also after large military manoeuvres", Poland Deputy Defence Minister Michal Dworczyk told the Polish PAP news agency. Russian Federation has said that some 12,700 troops will be involved but the actual figure is not certain.
NATO, however, believes - without evidence - that more troops will be involved.
Estonian Defense Minister Juri Liuk, however, says Moscow could deploy up to 100,000 troops. And depending on how aggressive a signal Russian Federation wants to send, it could choose to forgo the nuclear part of the exercises with this year's target: the fictional country of Veishnoriya, supposedly backed by the West and in coalition with two other fake nations of Lubeniya and Vesbasriya. International observers suggest that the invented countries are proxies for the Baltic States and Poland.