HOHENFELS, Germany — Less than three years after the United States Army sent home the last of its tanks that were permanently based in Europe, American commanders have been forced to rely on weapons shipped back temporarily or hardware borrowed from allies in the expanding effort to deter the latest threats from Russia with a fraction of the forces it had once deployed across the Continent.

That is part of an evolving mission as American commanders here are preparing, if called, to face off against a new set of threats — not only from an aggressive Moscow, but also from rising militancy and chaos in the Middle East. But with across-the-board spending cuts squeezing the Pentagon’s budget, and a war-weary nation showing little eagerness to sustain a global, war-ready crouch, one of the main targets in recent years has been the Army presence in Europe, a heavy land force in an increasingly digital combat zone.

Mustering the necessary troops and equipment for the mission here can be a challenge, said Lt. Gen. Ben Hodges, the Army’s commanding general in Europe. The number of permanently stationed soldiers on the Continent has dropped by 35 percent since 2012, and the Army has reduced some of its vehicles, weapons and support equipment or relocated it to other bases.

The Black Hawk helicopters used in a NATO exercise at the training center here in August, for instance, were rotated in for nine months from Fort Stewart, Ga., General Hodges said. Bringing over more helicopters requires either the multiple weeks to bring them by ship or the extra money to bring them by cargo plane.