Some 31,000 NATO troops are in Eastern Europe today for “Anaconda-2016,” which officials are describing as the single biggest war games held in the region since the Cold War, following months of NATO buildup which had similarly been likened to the Cold War era.

The operations are taking place mostly in Poland, with 14,000 US and 12,000 Polish troops the major contributors. The exercise is being described as the largest peace-time movement of foreign troops in Poland ever, and the first time since 1941 that German tanks will cross the country.

Early operations announced include a mass parachuting into the city of Torun, and military engineers scrambling to build a bridge over the Vistula River to help NATO assault vehicles advance eastward in this theoretical war.

The troops are advancing into NATO member Lithuania for the operation, but are heading in the general direction of the Russian exclave of Kaliningrad, a clear message that the operation is a simulation of a NATO invasion of Russian territory.

The biggest concern among NATO officials is the involvement of Poland’s “territorial army,” a makeshift paramilitary force built of gun club members and soccer hooligans. Two brigades of such forces are to “assist” in the operation.