Imam can refer to a religious leader who guides salat prayer services in a mosque, but also to a leader or ruler with political authority. Imam Shamil was a nineteenth century religious and military leader who fought against Russian armies of his homeland in present day Daghestan, which lies between Chechnya and the Caspian Sea. The inhabitants of the northern Caucasus had fought incursion by other rulers for centuries, against the Ottoman Empire in the fifteenth and sixteenth centuries and against Russia in the eighteenth and nineteenth centuries. After the deaths of the first and second Imams of Daghestan (Ghazi Mollah and Gamzat-bek), Imam Shamil took over the guerilla resistance to the Tsar's armies. Shamil became the third Imam of Daghestan and is known for his great physical strength and for his iron-fisted resistance to Russia.