The Persian campaign or invasion of Iran (Persian: اشغال ایران در جنگ جهانی اول) was a series of military conflicts between the Ottoman Empire, British Empire and Russian Empire in various areas of what was then neutral Qajar Iran, beginning in December 1914 and ending with the Armistice of Mudros on 30 October 1918, as part of the Middle Eastern Theatre of World War I. The fighting also involved local Persian units, who fought against the Entente and Ottoman forces in Iran. The conflict proved to be a devastating experience for Persia. Over 2 million Persian civilians died in the conflict, mostly due to the Armenian genocide by the Ottoman regime and Persian famine of 1917–1919, influenced by British and Russian actions. The Qajar government's inability to maintain the country's sovereignty during and immediately after the First World War led to a coup d'état in 1921 and Reza Shah's establishment of the Pahlavi dynasty.
^"Statistics of the Military Effort of the British Empire" (London: HMSO, 1920). Page 777. 2,050 British Army and 49,198 British Indian Army personnel sent to the "Persian Gulf Theatre" from India in total.
^Volkov, Denis V. (2022). "Bringing democracy into Iran: a Russian project for the separation of Azerbaijan". Middle Eastern Studies. 58 (6): 4. doi:10.1080/00263206.2022.2029423. S2CID246923610. The Russian military force, occupying not only Azerbaijan but the entire north and north-east of Iran, eventually amounted to almost twenty thousand by the outbreak of the First World War. After the opening of the so-called Persidskii front [the Persian front], which became the south flank of the First World War theatre, this number gradually grew to eighty or ninety thousand.
^"Statistics of the Military Effort of the British Empire" (London: HMSO, 1920). Page 778. South Persian Rifles not included. Figures may be underestimated. Details for British Indian Army in Persia: 25 Indian officers, 1,779 Indian other ranks, and 670 Indian followers dead from all causes. 11 officers, 454 other ranks, and 6 followers wounded.
^Erickson 2001, pp. 237–238, Appendix F. Battle casualties only. First invasion (1915): 200 killed, 400 wounded. Second invasion (1916): 85 killed, 276 wounded, 68 missing/captured. Defensive against British (1918): 500 killed, 1,000 wounded.
^The Ottoman Treatment of the Assyrians, David Gaunt, A Question of Genocide, ed. Ronald Grigor Suny, Fatma Muge Gocek, Norman M. Naimark, (Oxford University Press, 2011), 255;"In size, Halil's was definitely the superior force, but his army was badly mauled in a decisive battle near Dilman that left thousands of casualties on the battlefield."
^Savige, Stanley George (1920). Stalky's Forlorn Hope. Melbourne: McCubbin. p. 128.
^Ward, Steven R. (2014). Immortal, Updated Edition: A Military History of Iran and Its Armed Forces. Georgetown University Press. ISBN9781626160651., p.123: "As the Great War came to its close in the fall of 1918, Iran's plight was woeful. The war had created an economic catastrophe, invading armies had ruined farmland and irrigation works, crops and livestock were stolen or destroyed, and peasants had been taken from their fields and forced to serve as laborers in the various armies. Famine killed as many as two million Iranians out of a population of little more than ten million while an influenza pandemic killed additional tens of thousands."