Final answer:
Confederate forces fired upon Fort Sumter in Charleston's Harbor, marking the start of the Civil War and leading to a prolonged conflict with significant suffering.
Explanation:
The Civil War began when Confederate forces fired upon Fort Sumter in Charleston's Harbor on April 12, 1861. This attack marked the start of the Civil War between the Union and the Confederacy.
Both sides realized the conflict would not end quickly after the First Battle of Manassas, highlighting the underestimation of the war's duration and intensity.
The Union misjudged the Confederacy's resolve to secede, initiating a war characterized by great suffering for soldiers and civilians alike as Union forces advanced into Confederate territory.
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