The U.S. Army and its European allies are rehearsing a major land war in Germany. And they’re sending some of the sophisticated armored vehicles in the world.

Exercise Combined Resolve II is supposed to “replicate a complex operating environment” for NATO troops—that is, fighting a high-tech enemy with armor, artillery and other advanced equipment.

A high-tech enemy like Russia, which is still threatening to invade eastern Ukraine.

More than 4,000 troops from 13 nations are currently descending on American bases in Germany. The Pentagon says Combined Resolve II is its biggest European exercise planned for this year.

Notably, the Army is putting to use its new European Activity Set for the first time. The EAS is a stockpile of M-1A2SEPv2 Abrams tanks and M2A3 Bradley fighting vehicles, stored in warehouses at the Joint Multinational Training Command in Grafenwoehr, Germany.

The multi-million-dollar M-1A2SEPv2 is arguably the best tank in the world, with a powerful 120-millimeter cannon, a secret blend of shell-resisting armor and the latest sensors and communications.

The idea behind the activity set is that the tanks and other armored vehicles will always be in Europe, in top condition and ready for use. Armor crews from the U.S. can fly in, pull the vehicles out of storage and roll straight into training … or combat.

The EAS is supposed to make up for recent Army drawdowns in Europe that created a heavy armor gap. The Army’s last permanently-stationed tank units left Europe in 2013.