The Austrian Army were inactive during Operation Otto in 1938, in which Germany invaded Austria and annexed it. The Austrian military were integrated with the German military, and their first battle was the Invasion of Poland in September 1939. Most of the officers in the Austrian Army were generals in the German Army, since the Austrian soldiers were considered German troops. 950,000 Austrians served in the German Army, with 150,000 of them serving in the Waffen-SS. The other 800,000 operated as regular soldiers.