so ...
from what I understand of the last part
the "expedition" is basically to kill the people and lessen the mouths need to fed?
One of the reason the (later) Crusades were an "All Comers" affair.....
pre-Plague Europe was severely overpopulated for the technology of the time, with
far too many noble sons sitting idle without hope of inheriting or getting accolades..
So yes.... It isn't all that far-fetched to have anyone not needed for the status quo at home to "do their Duty" on a literal death march.