In 1618 Descartes was in the army of Prince Maurice of Nassau, the ruler of what's now this Low Country
[DOC] [TLE] Maurice, Prince of Orange - Wikipedia [PAR] Maurice of Orange (14 November 1567  23 April 1625) was stadtholder of all 
the provinces of the Dutch Republic except for Friesland from 1585 at earliest 
until his death in 1625.