The film reuses some of its battle footage (particularly the Battle of Britain and Dunkirk sequences) from Eagles Over London (1969) and The Inglorious Bastards (1978). Enzo G. Castellari, who directed those films, wasn't aware of the plagiarism and became very upset after seeing scenes from his movies in someone else's.
The German tanks in the climactic battle scene were US M-41 Walker Bulldog light tanks, built in 1951.
Ray Lovelock starred in Umberto Lenzi's previous World War II epic The Biggest Battle (1978), which has a very similar plot and structure.