Kammala wannan jumla: Hugo ya yi karatu a makarantar kwana da ke karkashin kulawar 'yan uwa mata a Aalbeke kuma ya fuskanci mamayar Jamus ta Belgium a lokacin Yaƙin Duniya na II. Kwarewar ta kasance mai tsarawa, kuma daga baya Claus zai daidaita shi a cikin littafinsa mai suna "The Sorrow of Belgium" (1983). Yawancin malaman Claus 'yan kishin Flemish ne wadanda suka nuna juyayi ga fascism, kuma Claus ya shiga reshen matasa na Jam'iyyar Flemish National Union. Mahaifinsa ma an tsare shi a takaice bayan da
'Yanci don haɗin kai. Mai nuna tausayi ga hagu na siyasa a wani lokaci mafi girma a rayuwarsa, Claus ya yaba da tsarin gurguzu bayan ziyarar Cuba a cikin shekarun 1960.