Proper defense against cannon was even less understood until the Civil War. If Louis xiv's military engineer Vauban had come to life during any battle or siege that followed his death up to 1861, he could easily have directed the Operations of the most advanced army engineers — whose fortifications, indeed, he would have found constructed on conventional lines according to his own text-books. Thus the gunner in Blue or Gray, and his comrade the engineer, were forced not only to fight and dig but to evolve new theories and practices. NO single work existed to inform the editors of this History systematically concerning that fight ing and digging. No single work described Federals and Con federates alike, and readably told the story of the great events with the guns and behind the ramparts from '61 to '65. That gap it is hoped this volume will fill.