The army originally consisted of fifteen divisions, the Artillery Reserve and the Cavalry Command. Commanded by Edwin Sumner, William B. Franklin, Louis Blenker, Nathaniel Banks, Frederick W. Lander, Silas Casey, Irvin McDowell, Fitz-John Porter, Samuel Heintzelman, Don Carlos Buell (Replaced by Erasmus Keyes in November, 1861), William F. Smith, Joseph Hooker, John A. Dix, Charles P. Stone (Replaced by John Sedgwick in February, 1862), George Stoneman (Replaced by Philip St. George Cooke in January, 1862), Henry J. Hunt and George McCall. Because this arrangement would be too hard to control in battle, President Lincoln issued an order on March 13, 1862, dividing the army into six corps headed by Sumner, Banks (despite being in the Shenandoah Valley and not part of the main army), McDowell, Heintzelman, and Keyes, the highest-ranking officers. McClellan was not happy with this, as he had intended to wait until the army had been tested in battle before judging which generals were suitable for corps command.