I remember when I was in ROTC I was told I could not be in the Chemical Corps because it was reclassified as a Combat Support and my eye sight precluded me. After commission I ended up in the Ordnance Corps (Service Support) and got assigned to a Reserve Infantry Training Division. When I became the Mobilization Officer for my Battalion, I got a chance to look at our mobilization plan for war. If the war with the Soviet Union got really bad, all officers in the Basic Training Companies, regardless of branch will become 11B’s (ie infantry) and the entire company of trainees upon completion of training (which can be abbreviated to two weeks) will become an infantry replacement unit for lost units. Things get bad, everyone regardless of eyesight, weight and age is infantry.
I love to hear contingency plans like that. Do you know of more?
Kinda like when TSHTF, the cooks will be formed into the "cannon fodder" brigade.