The Egyptian army’s disciplinary system made soldiers interchangeable across units.

Evidence

[The aim is to reach such a level of uniformity] that would allow any soldier on being moved from one unit to another or on being promoted to a higher rank to still be able to recognize the same system and not encounter what he is not accustomed to (la uṣādif … mā ughayyir ma’lūfiyatahu) … The basis of all military strength is order and complete obedience (al-niām wa kamāl al-ingiyād). — Khaled Fahmy, All the Pasha_s Men_ Mehmed Ali, his…, 742