I always get a chuckle out of that one. The lead, Richard Burton, is a Brit. His character is a Brit. They both speak like Brits. Yet he was sent on a mission to infiltrate a German fortress to liberate an Allied general.
Yet at no point does Burton speak with anything but a Brit accent. Even when he is on the phone speaking with a German general trying to prove/validate his false identity.
"I'm Richard Buuuuurton, damn you. I've done Shakespeare for the Queen and I'll play this part as I damned well please."
“Broadsword calling Danny Boy. Broadsword calling Danny Boy.”
That role was written especially for Richard Burton. Around that time Burton wanted to go into a new direction and do an action film. Alistair MacLean wrote that script for Burton.
Burton’s kids wanted him to do an action war movie and this was the one. It took Burton on a new direction. Big hit in 1968.