The credited director in English-language prints is Phil Karlson, but Italian prints list Karlson and Franco Cirino as co-directors. Cirino was a second-unit director who worked with American directors on films made in Italy and the Mediterranean. He also occasionally worked as an actor in them.
The film is based on a true World War II incident that occurred when the German army was making its last stand in Italy.
During World War II Sylva Koscina was a child in Yugoslavia and noted that she became very emotionally involved in this film because she saw so much death and destruction caused by the war there.
The name of the dam to be destroyed is Della Norte, which means "Dam of the North". The film is set, and was filmed, in northern Italy.