Beauregard's army in Northern Virginia was then known as the Army of the Potomac. In the latter part of July, its effective force was enumerated as 21,833 men and twenty-nine guns. But there was within reach of it the Army of the Shenandoah, numbering little less than nine thousand men.
This latter force was commanded by Gen. Joseph E. Johnston, a native of Virginia, who had distinguished himself in the Mexican war, and at the commencement of the present hostilities was at the head of the quartermaster's department in the United States Army with the rank of brigadier-general. Of the operations of his army in the Shenandoah Valley it is necessary to make a brief sketch, as these operations were a necessary part of the early campaign of the Potomac, and an obvious prelude to the great battle of the 21st July we are proceeding to relate.
In the latter part of May, Gen. Johnston assumed command of the Army of the Shenandoah, and, after a complete reconnoissance of Harper's Ferry and environs, he decided that the place was untenable, and, therefore, determined to withdraw his troops to Winchester. At this time Gen. Patterson was advancing, with a strong force, from Pennsylvania and Maryland into Virginia, and it was supposed that an attempt would be made by that general to form a junction in the Shenandoah Valley with Gen. McClellan, then advancing towards Winchester from the western parts of Virginia. To prevent this junction Gen. Johnston abandoned Harper's Ferry, on the 13th of June, after first burning the railroad bridge and such buildings as were likely to prove most useful to the enemy.
The Confederates retired to Winchester, but had scarcely arrived there when information was obtained that the Federals were still advancing; and Gen. Jackson-afterwards known as the immortal “Stonewall” Jackson — with his brigade, was sent to the neighbourhood of Martinsburg, to aid Stuart's cavalry in destroying what they could of the Baltimore and Ohio Railroad stock, and thus check the enemy's movements. On the 2d of July, however, Patterson succeeded in crossing the Potomac at Williamsport; the river being scarcely waist-deep there. Jackson fell back to Falling Waters, on the main road to Martinsburg, a running fire being kept up. A detachment of Federal troops was then sent forward to reconnoitre, and Jackson was encountered in a position where he had formed his men in line of battle, with four guns directly on the turnpike along which the enemy was advancing. For half an hour Jackson succeeded in maintaining his ground; but, at last, was compelled to fall back
