 This, coupled with growing Sunni disillusionment with what Hinnebusch calls "the regime's mixture of statism, rural and sectarian favouritism, corruption and new inequalities", fueled the growth of the Islamic movement.Because of this, the Muslim Brotherhood of Syria became the vanguard of anti-Ba'athist forces.The Brotherhood had historically been a vehicle for moderate Islam during its introduction to the Syrian political scene during the 1960s under the leadership of Mustafa al-Siba'i.