Ki Teitzei: Drafting Yeshiva students
My father, the Rav HaNazir, and Rav Tzvi Yehudah were of the opinion that everyone is obligated to go out and fight. This was a milhemet mitzvah, a compulsory war, in which all are expected to participate.
We haven't written up this one. Arutz Sheva - Israel National News has the full story — the link below goes straight to it.