In the first pitched battle of the Peninsula Campaign, nearly 41,000 Union troops and 32,000 Confederate forces were engaged in heavy fighting. Up until that point, this was the largest battle ever fought on American soil.

The battle had no clear winner; there was much attack and counter-attack by both sides. When Union Brigadier General Philip Kearny's division arrived, Kearny (who was missing an arm) led his men onto the field shouting, "I am a one-armed Jersey Son-of-a- Gun! Follow me!"