Persia, known today as Iran, is the second-largest country in the Middle East and the 18th-largest in the world (as at 2017). Historically, Iran was referred to as Persia by the West, due mainly to the writings of Greek historians who called Iran “Persis”, meaning "land of the Persians". It is the only country with both a Caspian Sea and an Indian Ocean coastline. The country's central location in Eurasia and Western Asia, and its proximity to the Strait of Hormuz, has always given it strategic importance.
Iran remained formally neutral throughout the war, but this did not stop it becoming entangled as a battleground for Russian, Turkish, and British troops. These battles destroyed many villages, killed several hundred Iranian civilians, and caused near-famine conditions that probably caused the death of several thousand more. The inability of the Iranian government to protect the country provoked rebellions and autonomy movements in northern Iran between 1915 and 1921. The British occupied much of the territory of western Iran, and fully withdrew in 1921. Major Cyril Sladden was in Persia from August 1918 to February 1919.