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.