Against whom or what did US soldiers fight in Vietnam? What was the NLF, the Viet Cong? What was the importance of pacification, and how did the military effort contribute to it? What was the role of the Vietnamese civilian population?

Against whom or what did US soldiers fight in Vietnam? What was the NLF, the Viet Cong? What was the importance of pacification, and how did the military effort contribute to it? What was the role of the Vietnamese civilian population?