In "A Treasury of Jewish Folklore" there's an English translation of a story that seems to be a fictional account of a former soldier who was part of Berek Yoselevitz's Jewish regiment in the Polish army, nicknamed "the Beardlings". The ex-soldier mentions that they were given permission to fight on Yom Kippur by a certain rabbi:
"We didn't leave the trenches even on Yom Kippur. Reb Meir absolved us...We sat in groups around small fires. Chatted, discussed Jewish learning..."
In the introduction to the story, it says that Berek received permission from the rabbi of Praga to fight on Shabbat. I assume it's the same rabbi.
Does anyone know who this Reb Meir was that gave this heter for fighting on Shabbat and Yom Kippur (and presumably also lighting fires for warmth)? Is there a discussion somewhere of his psak?