In 1938 Hitler demanded that Czechoslovakia allow its German-speaking Sudetenland region to be incorporated into Germany. This created an international crisis that resulted in the Munich Agreement in September, 1938, wherein Britain and France forced the Czechs to give up the Sudetenland without a fight in order to avoid war. As part of Hitler's overall plan to disassemble Czechoslovakia, the Munich agreement also required the Czechs to resolve the demands of other ethnic minorities through negotiations with neighboring Poland and Hungary. Subsequently, the eastern Czech regions of Slovakia and Subcarpathian Ruthenia declared themselves to be autonomous states, and Hungary pressed for the return of Czech lands it had lost in the Treaty of Trianon after WWI. Czechoslovakia's subsequent negotiations with Hungary concerning this issue failed, resulting in German and Italian arbitration, which resulted in the First Vienna Award in November, 1938. This settlement awarded the Czech regions of southern Slovakia and southern Carpathia to Hungary.
On March 13, 1939, Hitler informed Slovakia's leader that he was going to occupy the western Czechoslovakian regions of Bohemia and Moravia, and he suggested that Slovakia should declare total independence from Czechoslovakia and align itself with Germany or he would let the neighboring Hungarians occupy it. On March 14 the Slovaks declared their independence and on March 15 Hitler violated the Munich Agreement and occupied Bohemia and Moravia. That same day Subcarpathian Ruthenia, now called Carpatho-Ukraine, also declared its independence from Czechoslovakia. But Hungary immediately invaded Carpatho-Ukraine and conquered it in three days. The Hungarians were dissatisfied, however, with the new border they shared with Slovakia and launched an attack upon eastern Slovakia from Carpatho-Ukraine on March 23. Pressure from Hitler brought about a ceasefire on March 24, but some fighting continued until the March 31. This conflict brought about the first air combat to result from Nazi expansionism.
