Solution
The Civil War marked a ___defining____ moment in United States history. Long simmering sectional tensions reached a critical stage in 1860–1861 when eleven slave-holding states ___seceded___ and formed the Confederate States of America. Political ___disagreement____ gave way to war in April 1861, as Confederates ___insisted____ on their right to leave the Union and the loyal states refused to allow them to go.