This first volume of three discusses the tactical decisions made on day one and the ensuing combat, while also including a brief summary of the grand strategy in the Eastern Theater of the war, the conduct of the Pennsylvania Campaign from June 6 to 30, 1863, and the plight of civilians caught up in the conflict.

The Battle of Gettysburg, which took place July 1–3, 1863 in and around the town of Gettysburg, PA resulted in the largest number of casualties of the entire American Civil War and is seen as the key turning point in the conflict. On its first day, Confederate General Robert E. Lee's Army of Northern Virginia sought to destroy the Union army, forcing its men to retreat through the streets of the Pennsylvania town to the hills just to the south.

This volume, the first of three to cover the battle in depth, includes the morning cavalry skirmish, the morning clash at the Herbst's Woodlot and at the railroad cut, the afternoon clash at Oak Ridge, the afternoon fight at the Edward McPherson farm, the afternoon rout of the 11th Corps, the last stand of the 1st Corps at Seminary Ridge, the Union retreat through town, and the positions of the armies at nightfall.