Complex sentence: Not long after he published his narrative, tensions grew to an all-time high between the North and the South in the United States, and the Civil War began in April 1861 with the firing on Fort Sumter in South Carolina.
Split into simpler sentences: Not long after he published his narrative, tensions grew to an all-time high between the North and the South in the United States. The Civil War began in April 1861 with the firing on Fort Sumter in South Carolina.