In the winter of 1864 while Grant prepared for the inevitable spring campaign in Georgia, Congress revived the rank of lieu­tenant general for the purpose of giving it to its most victorious general. When the bill passed, President Lincoln called Grant to Washington to receive his commission and to assume command of all the armies.   Major General Henry W. Halleck, who became Grant' s chief of staff, then handled administrative matters and implemented the commander' s orders, thus creating a modern chain of com­mand and freeing Grant to take the field. Accompanying the Army of the Potomac, Grant planned a coordinated spring cam­paign of all the armies. Lincoln' s response to the plan-- " Those not skinning can hold a leg" -- delighted Grant. He soon learned, however, that some commanders, notably Major Gen­erals Nathaniel P. Banks, Benjamin F. Butler, and Franz Sigel, would let the legs slip from their grasp.   Grant' s arrival was greeted with scant enthusiasm by the Army of the Potomac. By not bringing in victorious generals from the western armies and by quietly conveying his confidence in his own troops, however, he soon raised morale. By the time his army crossed the Rapidan in early May it was ready for a series of bloody battles with General Robert E. Lee.   May ended with the armies massed for an encounter at Cold Harbor. Grant suffered heavy casualties but was determined to " fight it out on this line if it takes all summer." Evaluation of Grant' s success that May depends on whether one checks the maps or the casualty figures. Grant pushed Lee back to Rich­mond, but the cost was awesome.   Although Grant remained informed on the basis of reports sent to Halleck and copied for him, correspondence not ad­dressed to Grant has been excluded from this book unless it is essential to understanding Grant' s own letters. As he moved into Virginia, Grant' s correspondence increased in volume and significance. Halleck' s new position relieved Grant, and later his editors and readers, of much routine army business.