with the situation of refugees. League of Nations The first international co-ordination of refugee affairs came with the creation by the League of Nations in 1921 of the High Commission for Refugees and the appointment of Fridtjof Nansen as its head. Nansen and the commission were charged with assisting the approximately 1,500,000 people who fled the Russian Revolution of 1917 and the subsequent civil war (1917–1921), most of them aristocrats fleeing the Communist government. It is estimated that about 800,000 Russian refugees became stateless when Lenin revoked citizenship for all Russian expatriates in 1921. In 1923, the mandate of the commission was expanded to include the more than one million Armenians who left Turkish Asia Minor in 1915 and 1923 due to a series of events now known as the Armenian genocide. Over the next several years, the mandate was expanded further to cover Assyrians and Turkish refugees. In all of these cases, a refugee was defined as a person in a group for which the League of Nations had approved a mandate, as opposed to a person to whom a general definition applied. The 1923 population exchange between Greece and Turkey involved about two million people (around 1.5 million Anatolian Greeks and 500,000 Muslims in Greece) most of whom were forcibly repatriated and denaturalized from homelands of centuries or millennia (and guaranteed the nationality of the destination country) by a treaty promoted and overseen by the international community as part of the Treaty of Lausanne (1923). The U.S. Congress passed the Emergency Quota Act in 1921, followed by the Immigration Act of 1924. The Immigration Act of 1924 was aimed at further restricting the Southern and Eastern Europeans, especially Jews, Italians and Slavs, who had begun to enter the country in large numbers beginning in the 1890s. Most European refugees (principally Jews and Slavs) fleeing the Nazis and the Soviet Union were barred from going to the United States until after World War II. In 1930, the Nansen International Office for Refugees (Nansen Office) was established as a successor agency to the commission. Its most notable achievement was the Nansen passport, a refugee travel document, for which it was awarded the 1938 Nobel Peace Prize. The Nansen Office was plagued by problems of financing, an increase in refugee numbers, and a lack of co-operation from some member states, which led to mixed success overall. However, the Nansen Office managed