طالب ب demanded
إعادة the return, it's in the possessive so-->the return of
العسكريين military personnel
المسرحين released from service "al-musarra7een"
بسبب due to (or because of)
إلى العمل to work.
المسرحين بسبب الغياب is a restrictive clause; it could be placed within commas.
...demanded... the return of military personnel, released due to absenteeism, back to work.