Final answer:
The 10 southern states were divided into 5 military districts under the 1867 Military Reconstruction Act to protect freedmen and Republican sympathizers, enforcing martial law and overseeing the political reconstruction of the South.
Step-by-step explanation:
The 10 southern states were organized into 5 military districts to protect the freedmen and Republican sympathizers. This reorganization was part of the 1867 Military Reconstruction Act, which was a key element of the Reconstruction era following the Civil War. These districts were under martial law and commanded by Union generals, with the presence of federal troops to ensure the safety and rights of freed people and oversee the registration of voters and elections. States in these districts were required to write new constitutions and ratify the Fourteenth Amendment before rejoining the Union.