On the first day of the battle of Shiloh/Pittsburg Landing, General Albert Sidney Johnston, commander of the Department of the West is killed while leading an advance against a Union position in a peach orchard.
Union Brigadier General Robert McCook, ill and riding in an ambulance, is attacked by Confederate raiders between Athens, AL and Descherd, TN. He dies from his wounds.
Battle of Chantilly
Union Major General Phillip Kearny [US] is shot and killed when he crosses Rebel lines while riding his horse. Gen Issac I. Stevens [US] is also killed
Brigadier General Samuel Garland [CS] is mortally wounded during the Battle of Fox's Gap, dying later that day. Later that day, Major General Jesse Reno [US] is also mortally wounded a few feet from the spot where Garland fell.
General William A. Nelson gets into an altercation with General Jefferson C. Davis at the Galt House in Louisville, Kentucky. Davis returns later with a gun and shoots and kills Nelson.
General John Reynolds is killed west of Gettysburg, Pennsylvania. Less than a month earlier, Abraham Lincoln had offered him command of the Army of the Potomac
During the Battle of Atlanta, Major General James McPherson, commander of the Army of the Tennessee is killed when he accidently crosses Confederate lines.
Phil Sheridan [US], with a force of 40,000 men, strikes Jubal Early's [CS] 14,000 man Confederate army north of Winchester. Sheridan simply overpowered the Confederates. General Robert E. Rodes was mortally wounded in the conflict.