So he quickly naturalised himself and his son Pierre to Dutch citizenship .
When World War II came , Peter saw he had a potential problem , still having German citizenship , which was not unusual in this city so close to the German border .
So Peter quickly naturalised himself and Peter 's son Pierre to Dutch citizenship .
When World War II came , Peter saw he had a potential problem , still having German citizenship , which was not unusual in this city so close to the German border .