Cornelis van Geelkerken was born in Sint-Jans-Molenbeek, Belgium. In the 1920s he gravitated toward extreme nationalism. Proposing an authoritarian, anti-democratic movement to Anton Mussert they formed the Nationaal-Socialistische Beweging. He became director of their youth corps, the Nationale Jeugdstorm. After the German invasion Geelkerken was appointed Inspector-General of the Nederlandsche Landwacht (home guard set up to combat the Resistance). After the war he was sentenced to life imprisonment but released in 1959. He died on March 29, 1979 in Ede.