26 Men - "The Bells of St.Thomas" (1958)

Captain Rynning and several of his Rangers join a posse to smoke out the remnants of Luke Baxter's gang. The outlaws momentarily give the posse the slip and double back to take refuge in a mission school run for the reservation's Indian children and hold the priests and the youngsters as hostages.
https://www.imdb.com/title/tt0502358/plotsummary…

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