Festung Warschau 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 . 1939 . During the Invasion of Poland in 1939 the German troops reached the outskirts of Warsaw on September 9 . The Oberkommando des Heeres ( OKH ) assumed that the unfortified city damaged by countless terror bombing raids would be taken by German motorized units without any resistance and issued a press and radio release stating that the capital of Poland was taken . However , the German motorized assault was defeated and the advancing troops were forced to retreat with heavy casualties . From September 8 the city started to be referred to as " Fortress of Warsaw " in German broadcasts , which was to justify the aerial bombardment of civilian targets . The forces of the defenders , composed initially of only several battalion s and various units of second - line troops , were soon strengthened by the soldiers of the Armies " Poznań " and " Pomorze " that reached the city in the aftermath of the Battle of Bzura . The Germans laid a siege to the city and started shelling it with heavy artillery located in the outskirts . However , the defending troops managed to defeat all assaults and until the end of September the Germans could not manage to break into the city . After three weeks of constant aerial and artillery bombardment and assaults , the situation of the civilian inhabitants of Warsaw became dire . Food , water and medicine shortages as well as the Luftwaffe strafing inhabitants and refugees grouped within the city caused Warsaw ' s civilian authorities to request a cease - fire . Warsaw President Stefan Starzyński and Gen . Walerian Czuma , commander of the Warsaw garrison , decided that further resistance , although possible , would only expose the civilians to unnecessary hardship and signed the capitulation on September 28 , 1939 . The German text of the capitulation treaty as well as German propaganda used the term " Festung Warschau " to suggest that the failures of the Wehrmacht were due to heavily fortified terrain they had to cross . Warsaw , as a former Russian fortress , had several older fortifications , e . g . a ring of forts round the city and a citadel , built between 1835 and 1905 . But those fortifications failed to prevent the city from being overrun in World War I , as Warsaw was occupied by German and Austro - Hungarian troops in 1915 . 1944 . By 1944 the German Eastern Front ' s situation became hopeless . Adolf Hitler who took over personally many duties in the OKW and OKH ordered the " no step back " policy in an attempt to halt the Soviet offensives which could not be contained by open field battle anymore . Following this policy , several cities were declared " Festungen " ( " Fortresses " ) and were to be held by the German army at all cost , even if surrounded and with no hope to break the siege . Examples of this policy were the Festung Stalingrad and Festung Kiev . Later in the war , the " Festung " concept that was to be illustrated by the propaganda film " Kolberg " which reminds of that city ' s defense against Napoleon in 1807 , was also applied to German cities like Königsberg , Breslau , Frankfurt ( Oder ) and Berlin . Often even the civil population was supposed to support the rather suicidal attempts of defense , as the cities were largely destroyed in the course of the fights . On July 27 , 1944 Adolf Hitler ordered the " Festung Warschau " to be created and defended at all cost . The same day the governor of the General Government , Hans Frank , called for 100 , 000 Polish men between the ages of 17 – 65 to arrive at several gathering places in Warsaw the following day . They were to be employed at construction of fortifications for the Wehrmacht in and around the city . This move was viewed by the Armia Krajowa as an attempt to neutralize the underground forces , and the underground urged Warsaw inhabitants to ignore it . Fearing that the city would be turned into ruins and share the fate of Stalingrad and Kiev , General Tadeusz Bór - Komorowski ordered Operation Tempest to be started in Warsaw , which resulted in the Warsaw Uprising that lasted from August through September . After the Uprising , during which the Soviets troops had arrived near the Vistula , the Germans razed the city to the ground and continued the construction of concrete bunkers that were to defend " Festung Warschau " against the Red Army for four months . However , when the Soviets finally crossed the Vistula on January 17 , 1945 , the city was captured in several hours with little resistance from the remaining German garrison . The Chief of the Operational Branch of the German Army General Staff ( Generalstab des Heeres ) , Colonel Bogislaw von Bonin gave permission to the retreat of German Heeresgruppe A from Warsaw on January 16 , 1945 throughout the Soviet Vistula - Oder Offensive and was imprisoned on January 19 , 1945 by the Gestapo at Flossenbürg concentration camp and Dachau concentration camp as he rejected a direct command of Adolf Hitler by this action .