Sentence:  Then it was seen how perilous was the situation of the Boer snipers. . . . There was no escape for them save across the open. It says much for their courage that they took that perilous choice rather than <WSD>wave the white flag</WSD>, which would have ensured their safety. 
Meaning of the word marked with <WSD> tags:  To indicate to an opposing force that one is surrendering.