The four Reconstruction Acts passed by Congress (1867-68) outlined the conditions under which the Southern states would re-enter the Union, excluding Tennessee since it had already ratified the Fourteenth Amendment and was part of the Union.
One provision of this acts required the division of the ten Southern states (South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, Texas, Virginia, Arkansas, and North Carolina) into five military districts, that would be ruled by a Union general.
They would be divided this way until states approved the 14th Amendment (which ensured citizenship and equal rights for African Americans), drafted new state constitutions, both African and white Americans voted on them, and finally, the Congress approved the states constitution. Only then, states could be re-admitted.
