Edited sentence: About 80 percent of Assyrian clergy and spiritual leaders had perished, threatening the nation's ability to survive as a unit.In Iraq, the Assyrians joined the Kurds and Arabs in celebrating the Ottoman defeat, and joining the levies of the British Mandate of Mesopotamia.In late 1914 and 1915, the Ottoman Empire under the [[Young Turk regime declared a holy war on the Christians of the Empire along with the British and Russian Empires, who were all grouped together as the enemies of Islam.Ottoman Turks and Kurds proceeded to massacre tens of thousands of Assyrians in the Hakkari mountains of ancient Assyria (upper Mesopotamia, present-day southeastern Turkey) prior to any alliance between the Assyrians and the British or Russians.The Assyrian army under General David, the patriarch's brother, led the Assyrians out of an encircling Ottoman army manuever across the Persian border onto the plains of Urmia.The Assyrians, led by Assyrian general Agha Petros held them off.The Ottoman forces threatened Urmia and northwestern Persia after the Russian revolution in October 1917.The Patriarch of the Assyrians, Mar Shimun XIX Benjamin, declared war on the Ottomans on behalf of the Assyrian nation.Up to 100,000 Assyrians left Persia in 1918, but around half died of Turkish and Kurdish massacres and related outbreaks of starvation and disease.the Metropolitan and 150 merchants, and seized their goods as a reprisal for the plunderiuntil June 1918, at which point they were again encircled and had no choice but to break through to their British allies across the border in Mesopotamia