...fter the battle had been some hours in progress. A. P. Hill was sent for on the night of the 16th, and, leaving early on the 17th, reached the field, as we shall see, in time to snatch victory from Burnside 's corps. Thus, Lee, by great effort, concentrated all his army in time for participation in the battle. This concentration was, however, effected by exhausting marches and at the price of much st...