In real life no German prisoner of war held captive in Great Britain during World War II ever succeeded in escaping. One POW did however escape from a prison camp in Canada and made it back to Germany.
Though set in Scotland, this movie was predominantly filmed in Ireland.
The meaning and relevance of one of this movie's alternate titles, Wolfpack, refers to the large convoys of German Kriegsmarine U-boats which were used to mass-attack the Allies during World War II's Battle of the Atlantic. The Wolfpack or wolf pack term for the U-boats is likened from how U-boats hunted the Allied subs just as a pack of canine wolves live, feed, move, and hunt their prey in groups. The relevance is that many of the German prisoners-of-war in the McKenzie POW camp in the movie are captured Nazi German U-boat crew.
The meaning and relevance of McKenzie in this movie's title refers to the Second World War McKenzie Prisoner of War Camp in Scotland.
According to the book "Bill Collins Presents The Golden Years of Hollywood" by Bill Collins, this movie "...is very much a multi-national film. The setting is Scotland in World War II, although the film was made largely on location in Ireland with a cast of British, American, and German players, produced and directed by Americans."