Sentence:  But when a board of inquiry was called to look into the charges of cowardice made against him , the men who had seen Reno leave the <WSD>battlefield</WSD> and the officer who had heard Reno suggest that the wounded be left to be tortured by the Sioux , refused to say a harsh word against him . 
Meaning of the word marked with <WSD> tags:  a region where a battle is being (or has been) fought