The policy of dividing the South into military districts during Reconstruction primarily aimed to protect and provide opportunities for African Americans after the Civil War. Therefore, the most accurate response is:
It helped protect and provide opportunities for African Americans, but these successes were reversed when the policy ended.
This reflects the reality that while Reconstruction efforts initially brought some advancements in civil rights and opportunities for African Americans, many of those gains were rolled back in the subsequent years after federal military presence and policies were withdrawn.