In the sequel to his Mr. Lincoln's Army. Mr. Catton takes the Army of the Potomac, the determining body for the state of the Union, from the weakening battle of Fredericksburg in 1862 to the decisive turning point of Northern victory at Gettysburg in the spring of 1863. In Catton's former work, the disasters at Bull Run, Anteitam, with the Union army under the impetuous MacClellan are described. Later, Burnside at Fredericksburg, and Hooker at Chancellorsville both suffered defeats that only began to be repaired at Gettysburg. Catton reports these events with the historian's detachment and the vim of a modern legman. Headable and again, another gold mine for students of military strategy.