Under the rule of the Ottoman Empire, the six provinces/vilayets part of the geographic area of the Armenian Highlands were: Erzurum/Karin, Van, Mamuretül-aziz/Harput/Kharberd, Baghesh/Bitlis, Sebastia/Sivas and Diyarbekir/Tigranakerd. These regions were highly dominated by Armenian populations since ancient times. Today, these provinces make up Eastern Turkey and are referred to by Armenians as Western Armenia. Armenians also lived in the regions of historical Kilikia (Cilicia) in today’s Southern Turkey, and Constantinople which is today’s Istanbul.
An estimated 2.5 million Armenians lived in the Ottoman Empire before the Armenian Genocide. An approximate number of 1.5 million were killed between 1915-1923. Others were Islamized or exiled.