Sentence:  A mile back in the forest the tribe had heard the fierce challenge of the gorilla, and, as was his custom when any danger threatened, Kerchak called his people together, partly for mutual protection against a common enemy, since this gorilla might be but one of a <WSD>party</WSD> of several, and also to see that all members of the tribe were accounted for. 
Meaning of the word marked with <WSD> tags:  A group of people forming one side in a given dispute, contest etc.