Why didn't beauregard wait when he knew andreson was short on food?

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On April 12, 1861, General Beauregard sent Major Anderson a message saying that he would fire in one hour if Anderson didn't surrender. Anderson didn't surrender and the firing began. The South bombarded Fort Sumter from all sides. There were several forts surrounding Charleston Harbor that allowed the Southern forces to easily bombard Sumter. After many hours of bombardment, Anderson realized that he had no chance to win the battle. He was almost out of food and ammunition and his forces were badly outnumbered. He surrendered the fort to the Southern Army.