Serving in IDF (Israeli Defense Force)  is important from several angles. The major angle is the same reason why the Jewish community in Safed that was started by the disciples of the Gra organized a community protection force. It does not have to be any more profound than that. It also helps to know the important fact that both Reb Moshe Feinstein and Reb Aaron Kotler said in Israel "דינא דמלכותא דינא" (the law of the country is the law)
But it might be more profound that that.
But my claim is more simple. If all we had would be Reb Moshe and Reb Aaron Kotler that would be enough to establish the law.

My own feeling about this subject is mainly based on the little bit of reading I did about Jewish Communities during the Middle Ages. [That is in the Teshuvot of the teacher of the Rosh Rav Meir from Rotenberg]. Still there are troubles in Israel because of the Sephardim trying to get rid of the Ashkenazim. Not all but enough to make it worthwhile to be aware of this problem.