Sentence:  Selkirk persuaded eighty men and four officers to go to <WSD>Red</WSD> River where they were to serve as a military force to protect his settlers from the hostile Northwest Company which resented the intrusion of farmers into the fur traders ' empire . 
Meaning of the word marked with <WSD> tags:  a tributary of the Mississippi River that flows eastward from Texas along the southern boundary of Oklahoma and through Louisiana