It is a tragic irony that at the moment when one of Germany's most celebrated actors, Ulrich Mühe, had gained international fame for his performance in this year's Oscar-winning The Lives of Others he was to die of stomach cancer, aged 54. According to Florian Henckel von Donnesmarck, the director of the film, the original cause of the stomach problems that eventually led to cancer was the anxiety he suffered during the period when Mühe was a conscript in the East German military.
Assigned to patrol the Berlin Wall, he had - like all East German border guards - shoot-to-kill orders for fugitives trying to escape to the west, though, as far as is known, he never killed anyone.
Many years later, when Mühe had become a well-known stage, screen and television actor, he was an outspoken critic of the regime and helped to organise a major anti-government demonstration in East Berlin in November 1989, which led to the collapse of the wall.
Therefore, his role as the loyal Stasi officer in The Lives of Others was particularly meaningful. In fact, the part was written with Mühe in mind, which partly explains the extraordinary identification of the actor with the part. The way he gradually changes from a soulless, humourless party flunky, leading a cold, isolated existence, into a human being, is a remarkable piece of acting. The film won him seven prizes for best actor, including a European Film Award.
Born in the small town of Grimma in Saxony, the son of a furrier, Mühe trained as a builder before being drafted into the Volksarmee and detailed to watch the Berlin Wall. In 1975, aged 23, he began his theatre studies at the Hans Otto Theatre Academy in Leipzig and began to get small roles in Karl-Marx-Stadt (now, once again Chemnitz) before being discovered by Heiner Müller, a leading director and playwright in the German Democratic Republic (GDR) (obituary, January 1 1996), and invited to join the ensemble of the Berliner Volksbühne. Mühe's roles there included Goethe's Egmont, Ibsen's Peer Gynt, Hamlet in both the Shakespeare play and in Müller's modern masterpiece Hamletmachine (1979).
His film and television career began in 1983, but it was only after the fall of the Berlin Wall in 1989 that he began to get the parts he deserved. Mühe was first seen widely outside Germany as the gullible publisher Dr Wieland in the Oscar-nominated Schtonk! (1992), a farce on the Hitler diary hoax. The Austrian director Michael Haneke gave Mühe three choice roles. In Benny's Video (1992), he was the distant father partly blamed for his son becoming a "desensitised" killer, and in Funny Games (1997), he is the victim of young thugs, presumably for being an opera-loving bourgeois. Mühe carries conviction in both these specious studies of the cause and effects of violence, as he does as K in Haneke's adapation of Kafka's The Castle (1997).
In 1998, Mühe became a household name in Germany as the pathologist Doctor Robert Kolmaar in 73 episodes of the television crime series, The Last Witness. By this time he was married to Susanne Lothar, with whom he co-starred in about half a dozen films, including the three by Haneke. His second wife, whom he had married in 1984, was Jenny Grollman, with whom he acted in the early days. Years later, in a book describing the background to The Lives of Others, Mühe claimed that Grollman had informed on him to the East German secret service, which held hundreds of pages on him. She obtained an injunction against the publisher, swearing under oath that she was not an agent of the state.
In recent years, Mühe made a niche for himself as nasty Nazis - as Joseph Goebbels in Goebbels and Geduldig (2001), and Dr Mengele in Costa-Gavros's Amen (2002). He was scheduled to play Klaus Barbie in an upcoming feature. His last film was the truely dreadful comedy Mein Führer: The Truely Truest Truth about Adolf Hitler (2007), though Mühe was amusing as an actor hired to give Hitler lessons.
In November 2006 he appeared at the Barbican in Thomas Ostermeier's Berlin Schaubühne rendering of Blasted, by Sarah Kane, described by this newspaper's Michael Billington as a superb production.
Mühe is survived by Susanne Lothar and their two children, a daughter by Jenny Grollman and by two children from an earlier marriage.
· Ulrich Mühe, actor, born June 20 1953; died July 22 2007