The Diwan of Umar, assigning annuities to all Arabs and to the Muslim soldiers of other races, underwent a change in the hands of the Umayyads. The Umayyads meddled with the register and the recipients regarded pensions as the subsistence allowance even without being in active service. Hisham reformed it and paid only to those who participated in battle. On the pattern of the Byzantine system the Umayyads reformed their army organization in general and divided it into five corps: the centre, two wings, vanguards and rearguards, following the same formation while on march or on a battle field. Marwan II (740–50) abandoned the old division and introduced Kurdus (cohort), a small compact body. The Umayyad troops were divided into three divisions: infantry, cavalry and artillery. Arab troops were dressed and armed in Greek fashion. The Umayyad cavalry used plain and round saddles. The artillery used arradah (ballista), manjaniq (the mangonel) and dabbabah or kabsh (the battering ram). The heavy engines, siege machines and baggage were carried on camels behind the army.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): Who didn't change the Diwan of Umar?
unanswerable