NEVER CALL RETREAT The New York Times bestselling authors of Gettysburg continue their inventive series with this remarkable answer to the great "what-if" of the American Civil War:  After his great victories at Gettysburg and Union Mills, General Robert E. Lee's attempt to bring the war to an end by attacking Washington, D.C., fails. However, in securing Washington, the remnants of the valiant Union Army of the Potomac are trapped and destroyed. For Lincoln, there is only one hope left, that General Ulysses S. Grant can save the Union cause.   It is August 22, 1863. Pursuing the Union troops up to the banks of the Susquehanna, Lee is caught off balance when news arrives that Grant, in command of over seventy thousand men, has crossed that same river. The two armies finally collide in Central Maryland and a bloody weeklong battle ensues along the banks of Monocacy Creek. This must be the "final" battle for both sides.