The answer is: further democracy in the region.
Radical Republicans were committed to transforming Southern society after the Civil War. They believed that establishing an economy based on free labor would promote democratic principles by dismantling the old plantation system, which was heavily reliant on slave labor. This transformation was seen as essential for ensuring equal rights and opportunities for all citizens, particularly the newly freed African Americans.
While this was a potential outcome, it was not the primary goal of the Radical Republicans. They hoped that by promoting free labor, poor whites would see the benefits of a more egalitarian economic system and shift their political allegiances. However, the main focus was on restructuring the Southern economy and society to be more democratic and inclusive.
This was indeed a concern for the Radical Republicans, as they wanted to ensure that the South would not revert to its pre-Civil War ways, which could lead to further conflict. However, the primary method they believed would achieve this was through democratization and economic reform, rather than solely focusing on preventing future threats.
This was not a primary concern or goal of the Radical Republicans. Their focus was more on restructuring the Southern economy and society rather than addressing issues in the North.