In the German language, Festung Warschau ("Fortress Warsaw") is the term used to refer to a fortified and well-defended Warsaw. In the 20th century, the term was in use on three occasions during World War I and World War II. It was used when the Germans threw back the Russian advance in 1914, where Warsaw came within distance of the fighting in October. The term resurfaced during the September 1939 German invasion of Poland. Later in the second war, the term resurfaced between September 1944 and January 1945, when the retreating Germans tried to establish a defense in the city against the advancing Soviet Union.