Joseph, you must be blessed with unbelievable great age, because you were obviously there during the time of the Shoftim, the Malchei Yisroel and the Gemoro to know how combat was done in those days. Especially when the Sonei yisroel came to kill every person in a town. For me, I will be happy if hakodush boruch huh gives me 120 years.
I don’t see the relevance of the different groups in a war. The options of returning from war, etc, is only in a milchemet horeshus. In a milchement mitzvah there is no such option!! RAMBAM , hilchos melochim, seventh perek, fourth mishnah. this is where the Rambam clearly says “afilu choson…etc”. Tthere is no “petur” for learning Torah. In a war, EVERYONE must go out! Check out Shiras devorah on the possuk “Oiru meroz”.
there is no Rishon (or Acharon) in the world who frees people from defending Klal Yisroel in times of danger. Please supply real sources if you have them.