The North did not attack the South; it was the Confederates who initially succeeded from the Union and fired the first shot of the Civil War at Fort Sumter in 1861.
The North was obviously threatening to engage in war against the South over the slavery/secession issues. Whoever fired the first shot is immaterial.
The North was obviously threatening to engage in war against the South over the slavery/secession issues. Whoever fired the first shot is immaterial.