[779] evening. Contrary to his expectation, the Federals are strongly posted at this point: after having learned their strength he declines going any farther, and soon commences retracing his steps. The main purpose of his expedition is successful. The elements seem to conspire with him: a hard rain on the 16th swells Bull Run and deepens all the fords. The pontons, which Meade has immediately sent for, are with the great trains, parked far away; the roads are so bad that the crossings will not be reestablished in less than twenty-four or thirty-six hours.
Meade's plans are again altered on the morning of the 17th. Astonished at seeing the enemy show himself almost on his rear, he fancies that Lee is moving toward the Potomac and preparing a new invasion. He is not even undeceived on the evening of the 17th, when the enemy's cavalry stops pressing him. In his uncertainty he forms the resolution to still wait and to have Lee's positions felt by his cavalry. Therefore, only the latter cross Bull Run on the 18th.
At the same time, Lee gives to his army the order of retreat: it takes the same roads over which it has been marching a few days before, but in a contrary direction: almost all the wagons meet on the Warrenton road. Stuart remains to cover the roads between Groveton and Manassas; he will not hazard any serious battle on the left bank of Broad Run. Therefore, when Pleasonton's cavalry appears in force he orders his command to retreat slowly. The Unionists follow in two parallel directions: on the left, Merritt, who leads Buford's advance, reaches Bristoe about eleven o'clock in the morning, but is soon halted by the enemy's rear-guard; on the right, Kilpatrick has been ordered, but only at three o'clock in the afternoon, to march forward; at five o'clock he encounters the Southern cavalry near Groveton, and pushes it as far as Gainesville. But darkness soon interrupts the movements of the Federal cavalry; it has not been able to reach the main body of the enemy's army, which apparently is in full retreat.
Meade has at last seen his error: the pontons have arrived, and, besides, Bull Run is fordable; but it is too late to make up for the start that the enemy has. At daybreak the army moves forward in two columns, the Third and Sixth corps
