was count and (from 1674) prince of Nassau-Siegen, and Grand Master of the Order of Saint John (Bailiwick of Brandenburg). John Maurice joined the Dutch army in 1621, at a very early age. He distinguished himself in the campaigns of his cousin, the stadtholder Frederick Henry, Prince of Orange. In 1626 he became captain. He was involved in 1629 in the capture of Den Bosch. In 1636, he conquered a fortress at Schenkenschans.
