From the beginning of the appointment of Reza Khan as the minister of war, there was ever increasing tension with Zia ol Din Tabatabaee, who was prime minister at the time. Zia ol Din Tabatabaee wrongly calculated that when Reza Khan was appointed as the minister of war, he would relinquish his post as the head of the Persian Cossack Brigade, and that Reza Khan would wear civilian clothing instead of the military attire. This erroneous calculation by Zia ol Din Tabatabaee backfired and instead it was apparent to people who observed Reza Khan, including members of parliament, that he (and not Zia ol Din Tabatabaee) was the one who wielded power.