There is no key to civilization. The concept that native americans did not have a civilization or were not civilized is one only supported by the egotism and arrogance of the empirical profit oriented "conquerers" who have worked to eradicate all cultures that conflict with profits. The key to western civilization that allowed them to kill off the majority of the natives was a lack of respect for life and insane drive for control, ownership and dominance, to which the peaceful and sophisticated Natives would not stoop.
Answer: Its the third option The United States Colored Troops Regiments
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