June 26, from existing departments operating around Virginia, most of which had recently been outmaneuvered in Jackson's Valley campaign: Maj. Gen. John C. Frémont's Mountain Department, Maj. Gen Irvin McDowell's Department of the Rappahannock, Maj. Gen. Nathaniel P. Banks's Department of the Shenandoah, Brig. Gen. Samuel D. Sturgis's brigade from the Military District of Washington, and Brig. Gen Jacob D. Cox's division from western Virginia. The new army was divided into three corps of 51,000 men, under Maj. Gen. Franz Sigel (I Corps), replacing Frémont, who refused to serve under Pope (his junior in rank) and resigned his command; Banks (II Corps); and McDowell (III Corps). Sturgis's Washington troops constituted the Army reserve. Cavalry brigades under Col. John Beardsley and Brig. Gens. John P. Hatch and George D. Bayard were attached directly to the three infantry corps, a lack of centralized control that had negative effects in the campaign. Parts of three corps (III, V, and VI) of McClellan's Army of the Potomac and Maj. Gen. Ambrose Burnside's IX Corps (commanded by Maj. Gen. Jesse L. Reno), eventually joined Pope for combat operations, raising his strength to 77,000. On the Confederate side, General Robert E. Lee's Army of Northern Virginia was organized into two "wings" or "commands" (the designation of these units as "corps" would not be authorized under Confederate law until November 1862) of about 55,000 men. The "right wing" was commanded by Maj. Gen. James Longstreet, the left by Maj. Gen. Stonewall Jackson. The Cavalry Division under Maj. Gen. J.E.B. Stuart was attached to Jackson's wing. The Confederate organization was considerably simpler than the one Lee inherited for the Seven Days Battles; in that campaign there had been eleven separate divisions, which led to breakdowns in communications and the inability of the army to execute Lee's battle plans properly. William H.C. Whiting , Theophilus Holmes, Benjamin Huger, and John B. Magruder were all reassigned elsewhere. The command structure was reorganized as follows: Jackson's wing comprised his old Valley Army; the Stonewall Division (now commanded by Brig. Gen. Charles S. Winder) and Maj. Gen. Richard Ewell's division, plus the newly added command of Maj. Gen. A.P. Hill. Longstreet had seven divisions. His former command was divided into two parts led by Brig. Gens. Cadmus Wilcox and James L. Kemper. Maj. Gen. Richard H. Anderson got Huger's division, and Brig. Gen. John B. Hood was leading Whiting's Division due to