"We had avoided discovery by the Sioux scouts, and we were confident of giving them a complete surprise"

This quote by Buffalo Bill is describing a scenario in which he and his group had actually managed to avoid being found by Sioux scouts. This suggests that the Sioux scouts were trying to find them, and that Buffalo Bill and his group were trying to stay undetected. The quote likewise recommends that Buffalo Bill and his group were confident that they would be able to surprise the Sioux scouts. This could suggest that they had a strategy to ambush the scouts, or that they were positive that they might outsmart them. The quote indicates that Buffalo Bill and his group were in a harmful circumstance, however that they were positive that they could utilize their wits and ability to come out on top.