Rav Tzvi Yehuda said that if the Defense Minister would declare that everyone or a certain person is needed then it would be mandatory. Until then we need both- and the relationship is symbiotic (Sanhedrin 49a).
However, those learning must really be shteiging. Not hanging around. Not reading newspapers. Not going to chazzanut concerts. Learning three sedarim per day as well mornings on arvi Shabbatot.And have to pass periodic exams. During ben hazemanim they should do some volunteer work, preferably give shiurim to soldiers.