Assyrians were some of the British Administration's most loyal subjects, so they employed Assyrian troops ("Iraq Levies") to put down Arab and Kurdish rebellions in the aftermath of World War I and to protect the Turkish and Iranian borders of British Iraq from invasion. In consequence, Assyrians of all Christian denominations endured persecution under the Hashemites, culminating in the Simele massacre in 1933, leading thousands to flee to the West, in particular to the United States. Patriarch Shimun XXI Eshai himself went into exile in 1940–1941 and relocated the Patriarchate to Chicago which became the centre of the Assyrian–Chaldean–Syriac diaspora. However, the Assyrians who remained continued to work alongside the British, even playing a major role in bringing down the pro-Nazi Iraqi forces during World War II, and they remained attached to British forces until 1955.