▁present - day ▁Ira q . ▁ ▁Ira qi ▁Sh ia ▁pre ach ers ▁converted ▁the ▁Pers ians . ▁The ▁Sh ia ▁Saf avid ▁dynast y ▁declared ▁Sh ia ▁Islam ▁the ▁official ▁religion ▁of ▁Pers ia ▁in ▁ 1 5 0 1 . ▁▁ 1 5 th ▁and ▁ 1 6 th ▁centuries ▁The ▁B ani ▁S all ama , ▁T ay y ▁and ▁al - S oud an ▁in ▁the ▁Mes op ot am ian ▁Marsh es ▁were ▁converted ▁from ▁Sun ni ▁to ▁Sh ia ▁by ▁the ▁M ush a ' sha ' i yy ah ▁dynast y . ▁▁ 1 8 th ▁century ▁Ban u ▁Kh az al ▁was ▁converted ▁from ▁Sun ni ▁to ▁Sh ia ▁during ▁the ▁early ▁ 1 8 th ▁century . ▁Ban u ▁Ka ab ▁( including ▁its ▁Kh az raj ▁section ) ▁was ▁converted ▁during ▁the ▁mid - 1 8 th ▁century . ▁ ▁Late ▁ 1 8 th ▁to ▁mid - 2 0 th ▁century ▁Since ▁the ▁late ▁ 1 8 th ▁century , ▁most ▁of ▁Ira q ' s ▁Sun ni ▁Arab ▁tribes ▁converted ▁to ▁Sh ia ▁Islam ▁( part icular ly ▁in ▁the ▁ 1 9 th ▁century ). ▁During ▁the ▁ 1 9 th ▁century , ▁the ▁Ott oman ▁Empire ▁instit uted ▁a ▁policy ▁of ▁sett ling ▁the ▁nom adic ▁Sun ni ▁Arab ▁tribes ▁to ▁create ▁greater ▁central ization ▁in ▁Ira q . ▁The ▁tribes ▁adopted ▁a ▁sed ent ary ▁agricult ural ▁life ▁in ▁the ▁hinter lands ▁of ▁Naj af ▁and ▁Kar