With blue eyes and height of 6'2" (1.88m), Kahler was often chosen to play unsympathetic German characters or Nazis.
He appeared in the British production of the Adventures of Sherlock Holmes as the young Bohemian king in "A Scandal in Bohemia" and in "A Game of Shadows".
[4] One of his early roles was that of Kaiser Wilhelm II in Michael York's adventure film The Riddle of the Sands.
[8] In the Clint Eastwood spy thriller Firefox (1982), Kahler played KGB chairman Yuri Andropov.
Kahler played Herbert Kappler, a Nazi war criminal, who is befriended in his cell by a Vatican priest; the story is based on the real-life adventures of Monsignor Hugh O'Flaherty.