 In March 1946, Princen, like other young Dutchmen at the time, got a call-up order.He was to join the ranks of the Royal Netherlands Army and take part in what Dutch official histories still sometimes call "Police Actions" (politionele acties) but which became better known as the Indonesian National Revolution.Reluctant to take part in that war, Princen fled to France – but upon hearing that his mother was ill, came back and was arrested by the Marechaussee and detained at Schoonhoven.