What is Civil war ?
Civil war is (noun) a war between citizens inside a country COMMENT: The English Civil War, from around 1642 to 1651, was fought between supporters of the King (Charles I) and the supporters of Parliament, one of whose leaders was Oliver Cromwell. The king was captured, tried and executed in 1649, and Cromwell took the title of Lord Protector. The members of the King’s party were called Cavaliers, and the supporters of the Parliament were called Roundheads because they wore their hair cut short. The American Civil war of 1861 to 1865 was fought when eleven Southern states seceded from the Union (i.e. from the United States) and fought against the North under President Lincoln.
source: Easier English, Student Dictionary Upper Intermediate Level