This movie's title is taken from the expression "Hornet's Nest" meaning a violent or gravely contentious situation. In the film's case, this is relates to the the dangerous and difficult mission to blow up a dam protected by the Nazis. The expression is derived from the habitation for wasps or hornets, something which if disturbed can become a situation that presents itself with difficulty to the disturber.
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.