One of many 20th Century Fox releases to, strangely, have never been released on any home video format.
First released on June 26, 1964 in West Germany, in remembrance of the massive civil strike that the Danish began on that date in 1944, when the Nazis instituted curfew in Copenhagen, after a wave of sabotage.
Dalton Trumbo's son Christopher wrote in his father's biography that Trumbo wrote the screenplay "for $5,000 and using a pseudonym that he no longer remembered", during the time he was blacklisted. Film scholar Bernard F. Dick confirmed that Trumbo wrote the screenplay and that although the blacklist had been lifted by 1964, he still wanted to use a pseudonym. The exact roles of credited screenwriters Jack Davies and Michael Pertwee remain unclear, as well as the participation of uncredited Italian screenwriter Alberto Bevilacqua.