The Frierdiker Rebbe tells of one of the most difficult days he ever experienced. It was during the German bombardment of Warsaw, Poland.
He tells us how he hid in cellars, heard the bombs and finally the Shema Yisroel that all kinds of Jews shouted in unison when they thought they had been hit.
ספר השיחות קיץ ת"ש עמוד 11-12