The Secretary of War, Edwin M. Stanton, ordered the creation of two departments to organize these militia and defend Pennsylvania.
The headquarters were established in Pittsburgh, under the command of Maj. Gen. William T. H. Brooks, a combat veteran of the Union Army of the Potomac.
Brooks energetically set out to defend Pittsburgh, ordering citizens and railroad crews to build an elaborate network of earthworks and fortifications along key routes of approach that any invader might use.
Pennsylvania Governor Andrew Curtin sent 10,000 rifles, ammunition, and supplies to Pittsburgh, and Federal troops were hastily diverted to assist in the defense of the river town should it be threatened.
[2] General Brooks returned to active field command, leading a division in the XVIII Corps in the Army of the James.