[4] After acting as a film distributor, Hartwig's first film as a producer was the then controversial documentary Bis fünf nach zwölf – Adolf Hitler und das 3.
His first 15 films from 1957 to 1962 were economically based on original screenplays and did not use a major distributor.
[5] Hartwig began the next phase of his career in 1962 with The Hot Port of Hong Kong.
In 1977 Hartwig decided to film a large budget World War II film shot in Yugoslavia from the German point of view and engaged Sam Peckinpah to direct Cross of Iron.
[6] The film lead to a sequel Breakthrough (1979) directed by Andrew V. MacLaglen.