Rudolf Maister Day is celebrated in Slovenia in remembrance of the events at the end of the First World War, when the city council of Maribor proclaimed the annexation of Maribor to Austria. Maister disagreed with the decision, and he organized Slovenian volunteer forces of 4000 soldiers and 200 officers. In the night of November 23, 1918 this army under his command disarmed the security guards or the so-called green guard of Maribor Germans, and liberated Maribor.
In November and December Maister and his comrades in arms occupied the ethnic border area in Styria, thus preventing the annexation of Maribor with Styria and the Drava region to the German Austria.