A Defense Department release quoted Gen. Ray Odierno as saying the move is part of force restructuring due to the Budget Control Act.
The Army National Guard will cut 8,000 soldiers while the Army Reserve will skip a planned force increase and maintain its current size of 205,000.
General Odierno said the Army will shrink its active component end strength by 14 percent down to 490,000 troops from a wartime high of 570,000.
The 12 brigade teams set for inactivation include two teams in Germany at Baumholder and Grafenwoehr.
One brigade team will inactivate at each of 10 U.S. locations: Fort Bliss, Texas; Fort Bragg, N.C.; Fort Campbell, Ky; Fort Carson, Colo.; Fort Drum, N.Y.; Fort Hood, Texas; Fort Knox, Ky.; Fort Riley, Kan.; Fort Stewart, Ga., and Joint Base Lewis-McChord, Wash.
Odierno said the army is in the process of undergoing one of its largest organizational changes since World War II.