On the 5th of July General Johnson crossed the Potomac at Sharpsburg, where he met a small force of the enemy’s cavalry, which Lieutenant George M. E. Shearer, with a detachment of the First Maryland, pursued into Hagerstown, where coming suddenly upon a superior force he was compelled to retreat upon the main body.
In the pursuit which ensued Shearer was taken prisoner, along with several of his men.
General Johnson now shaped his course in the direction of Frederick, in the vicinity of which he awaited the arrival of Early, who overtook him on the 8th.
On the 9th, General Early dispatched General Johnson on a secret service by special order from General Lee. In this order he was directed to destroy communication between Baltimore and the North, threaten Baltimore, and break the railroad and cut the telegraph wires between Baltimore and Washington, and thence move on Point Lookout so as to attack on the morning of the 12th, when an attack was also to be made on the sea side. After releasing the prisoners, some fifteen thousand, he was to take command of them and rejoin Early at Bladensburg, whilst that General was in the meantime to attack Washington and carry it by assault.
Johnson moved his whole force to Cockeysville, and after destroying the bridges there he detached the First Maryland and Gilmor’s battalion, the two having been temporarily consolidated, and all under Colonel Gilmor’s command, and directed that officer to burn the railroad bridges over the Bush and Gunpowder rivers, which he did. Johnson then moved rapidly around Baltimore, and at Beltsville found a force of about one thousand of the enemy’s cavalry, which he charged and drove into Bladensburg, after which he started for Point Lookout, but had not gone many miles when he received an order from General Early to join him at once.
At Cockeysville Johnson had learned that the 19th corps of the enemy was landing at Locust Point, of which fact he at once advised Early, and it was this information which compelled the Confederate General to forego the intended raid on Point Lookout, and which had reached him just as he was about to assault Washington with his whole army.
In obedience to this order, General Johnson retraced his steps, and joined Early next morning at Blair’s house.
Early now turned his back on the Yankee capital, and directed his steps towards the Potomac, and crossed near Poolsville. In the retreat from Maryland, General Johnson was ordered to protect his rear. At Rockville he charged the enemy’s cavalry, and beat him, capturing eighty prisoners and horses. At Poolsville he was vigorously attacked in force, but drove his assailants back, and kept them in check until the whole army had recrossed the river.
It will thus be seen that General Johnson’s brigade constituted the advance guard in the invasion of Maryland, and the rear guard in the retreat. The Maryland troops were placed at the head of the column in the first and the rear in the latter; thus, from the 5th of July, the day of crossing, to the 14th, the day of recrossing the Potomac, they were almost constantly engaged, and always closest to the enemy.