Causes of the Civil War Although some historians feel that the Civil War was a result of political blunders and that the issue of slavery did not cause the conflict, they ignore the two main causes. The expansion of slavery, and its entrance The North didn't care about slavery as long as it stayed in the South. South Carolina seceded, because Abraham Lincoln, a Republican, was voted into office. The Republican party threatened the South's expansion and so Southerners felt that they had no other choice. The United States was divided into three groups by the time the Civil War began: those who believed