Many years ago, there was a young charedi yeshiva student called Nosson Slifkin. He wrote an essay in a book called Second Focus defending why charedim don’t go to the army. (It was based upon a presentation given by none other than R. Mordechai Neugroschel). The thrust of the essay was that the arguments about army service come down to nothing other than a theological dispute about certain metaphysical realities; namely, the role that the Torah requires charedi yeshiva students to stay in yeshiva as their role in national defense.
Twenty-five years later, I feel rather differently. First of all, after much study, it is clear to me that there is no traditional basis in Judaism for the idea that learning Torah replaces the obligation for national defense. But second, it is likewise clear that people who profess to believe otherwise only do so because it’s very convenient.
Charedim only profess to believe that Torah replaces hishtadlus, physical and material effort, when they can be sure that other people will do the physical and material effort. When they can’t offload it to other people, they do not believe that it is a replacement.
Hishtadlus for medicine - charedim do exactly the same as everyone else.
Hishtadlus against Covid - after R. Chaim Kanievsky's initial claim that Torah protects did not pan out, charedim did exactly the same as everyone else.
Hishtadlus for electioneering - charedim do exactly the same as everyone else.
Hishtadlus for government money - charedim do even more than everyone else.
Hishtadlus for immediate security threats (e.g. burglaries, threats to shuls) - charedim do exactly the same as everyone else.
Hishtadlus for war - charedim offload it to everyone else.
Anyone with intellectual honesty should recognize that the charedi worldview is a convenient contrivance - a fiction by which they avoid the immense sacrifice that others make on their behalf.
A full list of my posts on the topic of IDF service is at Torah and Army: The Big Index
Hishtadlus to solve the contradictions between Torah and Science - Chareidim offload it to someone else (named Nosson or Natan).
"Hishtadlus for war"
War if not a מצוה in itself, is wrapped up with many מצות.
And after the רמב"ם paskens:
וכל הנלחם בכל ליבו בלא פחד, ותהיה כוונתו לקדש את השם בלבד--מובטח לו שלא ימצא נזק ולא תגיעו רעה, ויבנה לו בית נכון בישראל, ויזכה לו ולבניו עד עולם, ויזכה לחיי העולם הבא
...it's preposterous to denigrate war and its accompanying מצות as mere השתדלות.
And then there's the description the גמרא of an ideal soldier:
עדינו העצני - כשהיה יושב ועוסק בתורה היה מעדן עצמו כתולעת, ובשעה שיוצא למלחמה היה מקשה עצמו כעץ
Does this sound like mere השתדלות?