Henry Warner Slocum Sr., was a Union general during the American Civil War and later served in the United States House of Representatives from New York. During the war, he was one of the youngest major generals in the Army and fought numerous major battles in the Eastern Theater and in Georgia and the Carolinas. While commanding a regiment, a brigade, a division, and a corps in the Army of the Potomac, he saw action at First Bull Run, the Peninsula Campaign, Harpers Ferry, South Mountain, Antietam, and Chancellorsville.

The Peninsula campaign of the American Civil War was a major Union operation launched in southeastern Virginia from March to July 1862, the first large-scale offensive in the Eastern Theater. The operation, commanded by Major General George B. McClellan, was an amphibious turning movement against the Confederate States Army in Northern Virginia, intended to capture the Confederate capital of Richmond. McClellan was initially successful against the equally cautious General Joseph E. Johnston, but the emergence of the more aggressive General Robert E. Lee turned the subsequent Seven Days Battles into a humiliating Union defeat.