After the battle of Gettysburg, Lee started for the Potomac, which he crossed with some difficulty, but with little interruption from the Federals, above Harper's Ferry, on July 14, 1863. The thwarted invader of Pennsylvania wished to get to the plains of Virginia as quickly as possible, but the Shenandoah was found to be impassable. Meade, in the mean time, had crossed the Potomac east of the Blue Ridge and seized the principal outlets from the lower part of the Valley. Lee, therefore, was compelled to continue his retreat up the Shenandoah until Longstreet, sent in advance with part of his command, had so blocked the Federal pursuit that most of the Confederate army was able to emerge through Chester Gap and move to Culpeper Court House. Ewell marched through Thornton's Gap and by the 4th of August practically the whole Army of Northern Virginia was south of the Rapidan, prepared to dispute the crossing of that river. But Meade, continuing his flank pursuit, halted at Culpeper Court House, deeming it imprudent to attempt the Rapidan in the face of the strongly entrenched Confederates. In the entire movement there had been no fighting except a few cavalry skirmishes and no serious loss on either side. On the 9th of September, Lee sent Longstreet and his corps to assist Bragg in the great conflict that was seen to be inevitable around Chattanooga. In spite of reduced strength, Lee proceeded to assume a threatening attitude toward Meade, and in October and early November there were several small but severe engagements as the Confederate leader attempted to turn Meade's flank and force him back to the old line of Bull Run. On the 7th of November, Sedgwick made a brilliant capture of the redoubts on the Rappahannock, and Lee returned once more to his old position on the south side of the Rapidan. This lay between Barnett's Ford, near Orange Court House (Lee's headquarters), and Morton's Ford, twenty miles below. Its right was also protected by entrenchments along the course of Mine Run. Against these, in the last days of November, Meade sent French, Sedgwick, and Warren. It was found impossible to carry the Confederate position, and on December 1st the Federal troops were ordered to recross the Rapidan. In this short campaign the Union lost sixteen hundred men and the Confederacy half that number. With the exception of an unsuccessful cavalry raid against Richmond, in February, nothing disturbed the existence of the two armies until the coming of Grant.