Five days later, Hooker, having become convinced that a large part of Lee's army was in motion toward the Shenandoah valley, proposed the daring plan of a quick and direct march to capture Richmond. But the President immediately telegraphed him a convincing objection: "If left to me, I would not go south of the Rappahannock upon Lee's moving north of it. If you had Richmond invested to-day, you would not be able to take it in twenty days; meanwhile, your communications, and with them your army, would be ruined. I think Lee's army, and not Richmond, is your true objective point. If he comes toward the upper Potomac, follow on his flank and on his inside track, shortening your lines while he lengthens his. Fight him, too, when opportunity offers. If he stays where he is, fret him and fret him." The movement northward of Lee's army, effectually masked for some days by frequent cavalry skirmishes, now became evident to the Washington authorities. On June 14, Lincoln telegraphed Hooker: "So far as we can make out here, the enemy have Milroy surrounded at Winchester, and Tyler at Martinsburg If they could hold out a few days, could you help them? If the head of Lee's army is at Martinsburg, and the tail of it on the plank road between Fredericksburg and Chancellorsville, the animal must be very slim somewhere. Could you not break him?" While Lee, without halting, crossed the Potomac above Harper's Ferry, and continued his northward march into Maryland and Pennsylvania, Hooker prudently followed on the "inside track" as Mr. Lincoln had suggested, interposing the Union army effectually to guard Washington and Baltimore. But at this point a long-standing irritation and jealousy between Hooker and Halleck became so acute that on the general-in-chief's refusing a comparatively minor request, Hooker asked to be relieved from command. The President, deeming divided counsel at so critical a juncture more hazardous than a change of command, took Hooker at his word, and appointed General George G. Meade as his successor.