The Union League and the Union Congressional Committee

The key Republican Party forces operating in the south at the time were the Union Congressional Committee and the Union League. What sort of people, both black and white, northern and southern, did they send out as organizers? How did they operate and navigate the dangers and opportunities that they encountered on the circuit? And then lastly, how did they engage in building black and Republican Party political power; power that led to black representation in state legislatures, in the US Congress and even statewide office?