The McKenzie Break

The McKenzie Break is a 1970 British war drama film directed by Lamont Johnson, starring Brian Keith as Jack Connor, an intelligence officer investigating recent disturbances at a German prisoner of war POW camp in Scotland. The POWs are led by the charismatic, yet ruthless, Willi Schlter Helmut Griem.

Connor believes the camp disturbances are a cover for an escape attempt. During a mass brawl two POWs escape dressed as British soldiers and Connor notices an outcast German POW named Neuchl Horst Janson, being dragged from the barracks and fleeing from the Germans. He is badly beaten and later that night in the hospital is strangled before Connor gets the chance to learn about Schlters plans.With Connor investigating the camp, Schlter leads his 28man escape party out of a tunnel the next day. Meeting the two escapees who have arranged a Uboat to pick them up, they all head for the coast. Unknown to Schlter, Connor has broken the code used in letters sent by POWs to Germany and knows the plan. ........

Source: Wikipedia