…The war that has broken out is truly fearsome, affecting every member of Klal Yisrael both physically and spiritually.  There is no doubt that Hashem has caused it to happen in order to arouse us to return to Him in complete repentance.  Therefore we are all obligated to beseech Hashem and pray that He saves us.

…It is the duty of each one of us to attend the Beis HaKnesses daily, to daven Shacharis, Mincha and Maariv there with our children, and to respond, “Amen, Yehei Shmei Rabba…” for, as the Midrash states, in this way countless harsh decrees are annulled each day.

It is impossible to fathom the number of salvation that could be brought about for Klal Yisrael if the inhabitants of each city were indeed to assemble in the Beis HaKnesses and daven together, and respond “Amen Yehei Shmei Rabba…” in unison every day.  In this way, thousands of people could be saved from death. ~ Michtavei Choftez Chaim, pp. 167, 169