The importance of Gaps in Virginia Mountains Virginia, early in the war, was the home ground of Stonewall's army, which the Confederacy took full advantage. The Union army, unfamilar with all the ways to cross mountains, were at a distinct disadvantage early in the war, when fighting in Virginia.
By 1863, through some painful experiences, the Union armies learned where the gaps were in Northern Virginia mountains.
For example, the Army of the Potomac blocked gaps in the Bull Run Mountains that prevented Stuart's Cavalry from getting to Pennsylvania on schedule, in 1863. From the reports, the Union officers seemed well familiar with Northern Virginia gaps, when following Lee back into Virginia after Gettysburg.
I haven't studied some of the western gaps in Virginia, but I know the army that knew where the gaps were, had a great tactical advantage over the army that did not know these gaps. |