Guy Fawkes fought for Catholic Spain during his military service in the Spanish Netherlands.
Fawkes left England and joined the Spanish forces fighting the Dutch Republic in the Eighty Years’ War. The conflict was shaped by the Dutch revolt against Spanish rule and by deep religious divisions between Catholic and Protestant powers. Fawkes served as a Catholic volunteer and became known for his military competence.
His time abroad connected him with continental Catholic networks and gave him practical knowledge of explosives and military engineering. Those skills later influenced Robert Catesby’s decision to recruit him for the plan to destroy the House of Lords.
Fawkes was not a Spanish national, and he did not serve as a regular English government soldier during this period. He was an English Catholic who volunteered with Spanish forces. This overseas service explains why some early accounts used his continental name, Guido Fawkes.