Fort Sumter was an unfinished fortification located in Charleston harbor that was strategically important for controlling access to the harbor. In April 1861, Confederate forces under General P.G.T. Beauregard opened fire on Fort Sumter, commanded by Union Major Robert Anderson, for 34 hours. Although outgunned with limited supplies, Anderson and his 85 soldiers held out for two days before surrendering due to lack of food and ammunition as Confederate forces had blocked resupply attempts. The bombardment and surrender marked the start of the American Civil War.