Southern Secession
Northerners believed that the national government's power was supreme over that of the states. Southerners felt that the abolition of slavery would destroy their region's economy. Northerners believed that slavery should be abolished for moral reasons.
The federal principle of government.
And federal means pertaining to or of the nature of a union of states under a central government distinct from the individual government of the separate states
Refused allied requests for their surrender
The answer to this question is Republic