Coffee addict: You are correct until a point, but surely you realize that there is a tremendous difference between a Nes Nigleh and a Nes Nistar. Now, everything related to the IDF so far have been Nisim G’luyim, but there is a scale. HBKH is much more willing (i.e. it takes far fewer Zechuyos from us or however these things work in HKBH’s Cheshbonos) to do Nisim the less G’luyim they are. Thus, the more people we have serving in the IDF the less Nigleh each Nes is and thus the more likely HKBH will perform it for us. Does that make any sense?
And all that aside, we are not supposed to rely on Nissim. Thus, having an army that can hold its own even without apparent Nissim probably has some value in its own right.