Combat roles are not the only option for serving in the IDF.
There are also important roles in: feeding soldiers,
distributing supplies to soldiers, helping the injured,
listening to enemy communications, and Cyber Security.
These non-combat roles could be filled by
Charedim who are not in yeshivah.
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Tractate Sanhedrin, page 72A:
“If you see someone coming to kill you, then arise and kill him first.”
In our times, Hamas and Hezbollah and Iran are obviously
coming to kill Jews, mostly in Eretz HaKodesh,
but also in other places, like the Iranian-back bombing
of the Jewish Community Center in Argentina in the 1990s.
Therefore, we are not merely permitted to
kill Hamas and Hezbollah before they kill more Jews;
we are obligated to do so, the same way we are
obligated to wear tefillin shel yad and tefillin shel rosh.