The Austrian resistance was launched in response to the rise of the fascists across Europe and, more specifically, to the Anschluss in 1938 and resulting occupation of Austria by Germany.
An estimated 100,000 people were reported to have participated in this resistance with thousands subsequently imprisoned or executed for their anti-Nazi activities. The main cipher of the Austrian resistance was O5, in which "O" indicates the first letter of the abbreviation of Österreich (OE), with the "5" indicating the fifth letter of the German alphabet (E). This sign may be seen at the Stephansdom in Vienna.