Carpathian Ruthenia during World War II Carpathian Ruthenia was a region in the easternmost part of Czechoslovakia ( Subcarpathian Ruthenia , or Transcarpathia ) that became autonomous within that country in September 1938 , declared its independence as the " Republic of Carpatho - Ukraine ” in March 1939 , was immediately invaded and annexed by Hungary , invaded by the Soviet Red Army in 1944 and incorporated into the Ukrainian Soviet Socialist Republic in 1946 . Independence and annexation by Hungary . In November 1938 , under the First Vienna Award which resulted from the Munich Agreement , Nazi Germany and Fascist Italy prevailed on the Second Czechoslovak Republic to cede the southern third of Slovakia and southern Carpathian Ruthenia ( now called Carpatho - Ukraine ) to the Kingdom of Hungary . Between 14 March and 15 March 1939 , the Slovak Republic formally declared its independence and Nazi Germany occupied Bohemia and Moravia creating the Protectorate of Bohemia and Moravia . On 15 March , Carpatho - Ukraine declared its independence as the Republic of Carpatho - Ukraine , with the Reverend Avhustyn Voloshyn as head of state . Hungary immediately invaded and annexed the new republic . On 18 March , resistance to the invasion ended . On 23 March Hungary annexed further parts of eastern Slovakia west of Carpatho - Rus . Soviet occupation . In October 1944 , Carpatho - Ukraine was taken by the Soviets . A Czechoslovak delegation under František Němec was dispatched to the area . The delegation was to mobilize the liberated local population to form a Czechoslovak army and to prepare for elections in cooperation with recently established national committees . Loyalty to a Czechoslovak state was tenuous in Carpatho - Ukraine . The Czechoslovak government - in - exile led by President Edvard Beneš issued a proclamation in April 1944 excluding from political participation former collaborationist Hungarians , Germans , and the Russophile Ruthenian followers of Andrej Brody and the Fencik Party ( who had collaborated with the Hungarians ) . This amounted to approximately one - third of the population . Another one - third was communist , leaving one - third of the population presumably sympathetic to the Czechoslovak Republic . Ukrainian Soviet Socialist Republic . Upon arrival in Carpatho - Ukraine , the Czechoslovak delegation set up headquarters in Khust and on 30 October issued a mobilization proclamation . Soviet military forces prevented both the printing and the posting of the Czechoslovak proclamation and proceeded instead to organize the local population . Protests from Beneš ' s government - in - exile went unheeded . Soviet activities led much of the local population to believe that Soviet annexation was imminent . The Czechoslovak delegation was also prevented from establishing a cooperative relationship with the local national committees promoted by the Soviets . On 19 November , the communists , meeting in Mukachevo , issued a resolution requesting separation of Carpatho - Ukraine from Czechoslovakia and incorporation into the Ukrainian Soviet Socialist Republic . On November 26 , the Congress of National Committees unanimously accepted the resolution of the communists . The Congress elected the National Council and instructed that a delegation be sent to Moscow to discuss union . The Czechoslovak delegation was asked to leave Carpatho - Ukraine . Negotiations between the Czechoslovak government and Moscow ensued . Both Czech and Slovak communists encouraged Beneš to cede Carpatho - Ukraine . The Soviet Union agreed to postpone annexation until the postwar period to avoid compromising Beneš ' s policy based on the pre - Munich frontiers . After World War II , in June 1945 , Czechoslovakia and the Soviet Union signed a treaty ceding Carpatho - Ruthenia to the Soviets . Czechs and Slovaks living in Carpatho - Ukraine and Ukrainians ( Ruthenians ) living in Czechoslovakia were given the choice of Czechoslovak or Soviet citizenship . In 1946 the area became part of the Ukrainian Soviet Socialist Republic , as the Zakarpattia Oblast ( ' Transcarpathian Oblast ' ) . Impact on Hungarian population . The end of the war was a cataclysm for the ethnic Hungarian population of the area : 10 , 000 fled before the arrival of Soviet forces . Many of the remaining adult men ( 25 , 000 ) were deported to the Soviet Union ; about 30 % of them died in Soviet gulags . As a result of war losses , emigration and extermination of Hungarian - speaking Jews , the Hungarian - speaking population of Carpathian Ruthenia decreased from 161 , 000 in 1941 ( Hungarian census ) to 66 , 000 in 1947 ( Soviet census ) ; the low 1947 number is doubtless in part a result of Hungarians ' fear to declare their true nationality .