‘Assuredly,’ said Kurruk Shah with a grim chuckle. ‘Otherwise, why did I, who have served the Queen for seven-and-twenty years, and killed many hill-dogs, shout aloud for quarter when the lightning revealed us to the watch-towers? When I was a young man I saw the killing in the valley of Sheor-Kot there at our feet, and I know the tale that grew up therefrom. But how can the ghosts of unbelievers, prevail against us who are of the Faith?
This is from "Lost Legion" by Rudyard Kipling.
https://www.kiplingsociety.co.uk/tale/the-lost-legion.htm
I don't understand the meaning of
shout aloud for quarter
I am glad if someone would kindly teach me.