Main actors were cast because of their close physical resemblance to the real-life soldiers they were portraying.
At the beginning of the movie (aerial shot) you can see a mound where Monument of Westerplatte was build at the time of making movie.
Defenders of Westerplatte: Leonard Piotrowski, Stefan Grodecki and Michal Gawlicki were historical consultants of the movie.
Movie is based on memories of defenders of Westerplatte collected by Zbigniew Flisowski. He was author of the book "Westerplatte" and historical consultant of the movie.