The shortest battle in the US Civil War was the Battle of Fort Sumter, which lasted only about 34 hours from April 12 to April 13, 1861.
Fort Sumter, located in Charleston Harbor, South Carolina, was the site of the first shots fired in the Civil War. After the secession of Southern states from the Union, Confederate forces demanded the surrender of the fort, which was held by Union troops. When negotiations broke down, Confederate artillery opened fire on the fort in the early morning hours of April 12. The Union garrison, under the command of Major Robert Anderson, returned fire but was ultimately unable to hold the fort.
The battle concluded with the Union troops surrendering Fort Sumter on April 13, marking a significant event that ignited full-scale warfare between the North and South. The rapid engagement and subsequent surrender classify it as the shortest battle of the war, but it also set the stage for a conflict that would last for four long years.