There is a precedent in Jewish history for the correct approach to warfare. In the Midbar, 1000 from each Shevet went to fight. In the times of Dovid Ha’Melech, there was a rotation. One third fought while the other 2/3 remained behind to Daven and learn for the Hatzlacha of those on the front lines.
In my Yeshiva, during times of active war, the R”Y puts a sign-up sheet on the wall. It is for Bachurim and Avreichim to accept hours of learning Chok v’Lo Ya’avor from 6:00 AM until 12:00 midnight. He explains that it should really be round the clock, but he hesitates giving the Yetzer Hara foothold to destroy the Sedarim of the Yeshivah. He also gives strong Musar regarding the strengthening of Hasmada during Sedarim. If we are partners in protection, then we have to step up our efforts when the battle rages!
My message to any Jew in E”Y who is not learning full-time is: We need you! There are so many missing from the two-thirds necessary to protect the rest! I eagerly await the time when our ranks are full and I too can take my turn on the front lines. Until then, I must remain in the breach where there are not enough men!