The institution of African slavery, as it existed in about half the States of the Union, and the contests pervading the public mind for many years, between those who desired its curtailment and ultimate extinction and those who desired additional safeguards for its security and perpetuation, culminated in the effort, on the part of most of the States in which slavery existed, to separate from the Federal government, and to resist its authority. This constituted the war of rebellion, and whatever auxiliary causes may have contributed to bring about this war, undoubtedly the overshadowing and efficient cause was African slavery.