At Early's suggestion General Lee authorized him to move north at an opportune moment, cross the upper Potomac into Maryland and threaten Washington.

Indeed, General Lee had foreshadowed such a course when Early started toward Lynchburg for the purpose of relieving the pressure in front of Petersburg, but was in some doubt as to the practicability of the movement later, till persuaded to it by the representations of Early after that general had driven Hunter beyond the mountains and found little or nothing opposing except the small force of Sigel, which he thought he could readily overcome by celerity of movement.
By rapid marching Early reached Winchester on the 2d of July, and on the 4th occupied Martinsburg, driving General Sigel out of that place the same day that Hunter's troops, after their fatiguing retreat through the mountains, reached Charlestown, West Virginia.

Early was thus enabled to cross the Potomac without difficulty, when, moving around Harper's Ferry, through the gaps of the South Mountain, he found his path unobstructed till he reached the Monocacy, where Ricketts's division of the Sixth Corps, and some raw troops that had been collected by General Lew Wallace, met and held the Confederates till the other reinforcements that had been ordered to the capital from Petersburg could be brought up.

Wallace contested the line of the Monocacy with obstinacy, but had to retire finally toward Baltimore.

The road was then open to Washington, and Early marched to the outskirts and began against the capital the demonstrations which were designed to divert the Army of the Potomac from its main purpose in front of Petersburg.
Early's audacity in thus threatening Washington had caused some concern to the officials in the city, but as the movement was looked upon by General Grant as a mere foray which could have no decisive issue, the Administration was not much disturbed till the Confederates came in close proximity.