West Virginia (part one):
The beginnings of Confederate weakness in the war were apparent as early as May 12, 1861 when a Union force under General Milroy sent from Washington, DC took Harper's Ferry, destroying the Confederate garrison stationed there. In control of the ferry, the Union began to build up its forces in the region.
Battle of Clarksburg:
Further West, on June 15, General Lew Wallace led a force of 9715 infantry, 2789 cavalry and 26 artillery against General Floyd in Clarksburg, WV. Wallace lost 510 infantry, 4 cavalry and 2 artillery, while Flloyed's force of 4847 infantry, 2414 cavalry, and 15 artillery lost 676 infantry and 335 cavalry and was forced to retreat from the region, losing an additional regiments worth of men in the initial stages of the retreat. This began the races of West Virginia where retreating Confederate forces and advancing Union forces fought a series of skirmishes. In late June, a Confederate cavalry screen won a small skirmish in Lewisburg, but in July, Stone moved a force of Marylanders into Clarksburg and found and struck Floyd's retreating force agaim, now under General Thompson. Around the same time, Union General Hurlburt moved on Charleston, WV, defeating a segment of Wise' force there with 4500 Ohio and West Virginia men against about 4000 Confederates. In August, Stone won another skirmish against Thompson in the vicinity of Calhoun. In August, Floyd brought 10,000 against McCall in Lewisburg, who retreated, but the Confederate force was soon forced to retreat out of the state and by the end of the year, the Union had divisions under McCall and Hurlburt garrisoning southern West Virginia.
First Battle of Harper's Ferry:
The force under Wallace and Mannsfield, which had won the battle of Clarksburg in June, quickly returned east to garrison Harpers Ferry. On July 12, Joe Johnston attacked the again augmented Union defenses at Hapers Ferry, still under General Milroy. Milroy had 17510 infantry, 1723 cavalry, and 61 artillery and lost 2552 infantry and 122 cavalry. Johnston had 22, 862 infantry, 6120 cavalry, and 43 artillery and lost 3487 infantry and 762 cavalry, and the Union had won the first battle of Harper's Ferry, and its first major battle in the war. By the end of the battle, Milroy's force was tired but not defeated. New soldiers were sent to replace casualties in his regiments and when they saw how slow Milroy's force worked, gave them the nickname, "Milroy's weary boys", a name which they came to embrace due to the hard labor they were willing to endure even after Milroy moved to command another force.
General McClellan served the initial part of the war on the Ohio/West Virginia border training soldiers who succeeded in capturing New Madrid, Missouri and West Virginia. For his success, he was put into command at Harper's Ferry, with Milroy moved to command the forces in southern West Virginia.
Second Battle of Harper's Ferry:
On October 6, Johnston attacked Harper's Ferry again with 30129 infantry, 6163 cavalry, and 41 artillery against McClellan's reinforced corps of 24,678 infantry, 3830 cavalry, and 72 artillery. Johnston lost the battle, 5557 infantry, and 488 cavalry, while McClellan lost 4797 infantry and 244 cavalry, but won the day.