Iraqis form one of the largest diasporas in the world. The Iraqi diaspora is not a sudden exodus but one that has grown rapidly through the 20th century as each generation faced some form of radical transition or political conflict. From 1950 to 1952 Iraq saw a great exodus of roughly 120,000 - 130,000 of its Jewish population under the Israel-led "Operation Ezra and Nehemiah". There were at least two large waves of expatriation of both Christians and Muslims alike. A great number of Iraqis left the country during the regime of Saddam Hussein and large numbers have left during the Second Gulf War and its aftermath. The United Nations estimates that roughly 40% of Iraq's remaining and formerly strong middle-class have fled the country following the U.S.-led invasion in 2003.