Whether the IDF is saving Jewish lives is subject to debate. The contrary argument is that by having launched a avoidable war against the Muslims, they have endangered Jewish lives, and it is not a “milhemes mitzvah” but rather a “milhemes stus”. From this perspective, Hareidi Jews would be no worse off under an Islamic regime than under the zionist regime (and if that occured, we wouldn’t be dealing with a government that encourages mass abortion of Jewish babies, or engages on religious coercion on Jews to give up Torah and Mitsvos). Muslims historically tolerated Jews as long as we were content to be “second class citizens” which we usually were and in all fairness what we are in Eretz Yisrael.
For some with the above view, the IDF should regard them as conscientious objectors and should make no attempt at conscription, and the only sanctions for non-service in the army should be those used against Israeli Arabs who don’t serve in the army.
For those who disagree with the above, i.e., support the zionist state in spite of it being non-frum, there are still the issues of the relative importance of learning Torah versus playing soldier, and the issue of non-accomodation of religious practices in the IDF (which varies widely between units). These are separate issues.