I consider the fact that Muslims are at war with Israel, puts Israel in a defensive position. And as we see in the Talmud in Eruvin [as brought in the Rambam] this is something for which that one can carry on Shabat. It this puts it in the category of Milchment Mitzvah . At any rate we can safely say it is a mitzvah. And we know the Halacha that if there is before a person two mitzvot: (1) Learning Torah, and (2) Another mitzvah (even the smallest mitzvah), then one has to stop learning to do the mitzvah.
In conclusion, people that do not serve in IDF are not kosher Jews.
And the Ultra religious that object to this are not on the level of the Rambam to be able to disagree with this. And frankly, most of them don't know how to learn anyway. [Just because they dress up like with black clothing does not mean they can learn.] So why even care about what they say?
[ Ultra Orthodox are going with the idea of the super-organism to decide and not on actual Halacha. What I mean is that Ultra religious have been trying to form a super-organism called Ultra religious which would in theory be divided into two parts. One would form the ruling Brahmin class of the Jewish people. Then there would be the untouchables, the secular Jews, who would be supporting them by hard labor. This model of the Jewish people is not based on the Torah, so it is no surprise that many Jews in Israel are not in favor of it.]
