Iran once ruled modern day Eastern Georgia .
`` `` '' The Islamic World to 1600 '' '' , The Applied History Research Group , The University of Calgary , 1998 , retrieved 1 October 2007 Functioning again as a leading power , this time amongst their neighboring Ottoman arch rival for centuries , Iran had been a monarchy ruled by a shah , or emperor , almost without interruption from 1501 until the 1979 Iranian revolution , when Iran officially became an Islamic Republic on 1 April 1979.Iran Islamic Republic , Encyclop�dia Britannica retrieved 23 January 2008Encyclop�dia Britannica 23 January 2008Over the course of the first half of the 19th century Iran lost many of its territories in the Caucasus ( which it had been ruling intermittently encompassed for millennia ) , comprising modern day Georgia , Dagestan , Azerbaijan , and Armenia , to its rapidly expanding and emerged neighboring rival the Russian Empire , following the Russo-Persian War ( 1804-1813 ) and Russo-Persian War ( 1826-1828 ) .Timothy C. Dowling Russia at War : From the Mongol Conquest to Afghanistan , Chechnya , and Beyond pp 729 ABC-CLIO , 2 dec . ''
History of Iran