The Munich Agreement was reached in Munich on 30 September 1938, by Nazi Germany, the United Kingdom, France, and Italy. The agreement provided for the German annexation of part of Czechoslovakia called the Sudetenland, where three million people, mainly ethnic Germans, lived. The pact is known in some areas as the Munich Betrayal (Czech: Mnichovská zrada; Slovak: Mníchovská zrada), because of a previous 1924 alliance agreement and a 1925 military pact between France and the Czechoslovak Republic.
Germany had started a low-intensity undeclared war on Czechoslovakia on 17 September 1938. In reaction, Britain and France on 20 September formally requested Czechoslovakia cede the Sudetenland territory to Germany. This was followed by Polish and Hungarian territorial demands brought on 21 and 22 September, respectively. Meanwhile, German forces conquered parts of the Cheb District and Jeseník District, where battles included use of German artillery, Czechoslovak tanks, and armored vehicles. Lightly armed German infantry briefly overran other border counties before being repelled. Poland grouped its army units near its common border with Czechoslovakia and conducted an unsuccessful probing offensive on 23 September. Hungary moved its troops towards the border with Czechoslovakia, without attacking. The Soviet Union announced its willingness to come to Czechoslovakia's assistance, provided the Red Army would be able to cross Polish and Romanian territory; both countries refused.