Final answer:
The KKK aimed to suppress African American rights and uphold white supremacy, thus undermining Reconstruction by instilling fear and violence to maintain racial hierarchies.
Step-by-step explanation:
The purpose of the Ku Klux Klan (KKK) according to General Thomas was to suppress African American political and economic power, protect the pre-war social order, and maintain white supremacy. This mission directly undermined Reconstruction efforts by terrorizing African Americans and other supporters of Reconstruction to deter them from exercising their citizenship rights and freedoms. Tactics used by the KKK included violence, intimidation, and even assassination to achieve their goals of keeping blacks, and to some extent 'low' whites, subservient.
The Klan's activities effectively hindered the progress of Reconstruction by undermining the federal government's attempts to protect the civil rights of newly freed slaves and by restoring a white-dominated society. Their actions included burning schools, preventing African Americans from voting, and perpetrating violent acts against individuals they considered troublemakers or threats to their vision of society.