Only a few brigades of Lee's infantry guarded the works along the river, the bulk of it being so situated that it could be thrown to either flank toward which the Union troops approached.
General Grant adopted the plan of moving by his left flank, with the purpose of compelling Lee to come out from behind his intrenchments along Mine Run and fight on equal terms.

Grant knew well the character of country through which he would have to pass, but he was confident that the difficulties of operation in the thickly wooded region of the Wilderness would be counterbalanced by the facility with which his position would enable him to secure a new base; and by the fact that as he would thus cover Washington, there would be little or no necessity for the authorities there to detach from his force at some inopportune moment for the protection of that city.
In the move forward two divisions of my cavalry took the advance, Gregg crossing the Rapidan at Ely's ford and Wilson at Germania ford.
Torbert's division remained in the rear to cover the trains and reserve artillery, holding from Rapidan Station to Culpeper, and thence through Stevensburg to the Rappahannock River.

Gregg crossed the Rapidan before daylight, in advance of the Second Corps, and when the latter reached Ely's ford, he pushed on to Chancellorsville; Wilson preceded the Fifth Corps to Germania ford, and when it reached the river he made the crossing and moved rapidly by Wilderness Tavern, as far as Parker's Store, from which point he sent a heavy reconnoissance toward Mine Run, the rest of his division bivouacking in a strong position.

I myself proceeded to Chancellorsville and fixed my headquarters at that place, whereon the 5th I was joined by Torbert's division.
Meanwhile, General Meade had crossed the Rapidan and established his headquarters not far from Germania ford.

From that point he was in direct communication with Wilson, whose original instructions from me carried him only as far as Parker's Store, but it being found, during the night of the 4th, that the enemy was apparently unacquainted with the occurrences of the day, Meade directed Wilson to advance in the direction of Craig's Meeting House; leaving one regiment to hold Parker's Store.