Most famous German transport plane of World War 2 Ju 52 was easily recognizable because he had characteristic three engines (one fitted in the nose and two on the wings). It started as civilian passenger carrier all over Europe, but during the war it was widely used to transport German troops, officials, medical evacuation and air supply. In early 1930s one of the versions was adapted to be a level bomber, but when modern bombers like He 111 or Do 17 were introduced the concept of Ju 52 bomber was quickly dropped.
Small unit of commandos is dropped in the Alps, where they have to infiltrate the castle on the top of a mountain. Their mission seems to be impossible to fulfil, but British intelligence selected their best men for the job.