They dared return - Patrick K. O'Donnell

It's July 1943. Frederick Mayer, a German-born Jew is recruited to secret operations unit, the OSS. Along with 4 other German-Jews, he volunteers for behind-enemy-lines operations. All have family members in concentration camps. All want revenge.
Mayer and his comrades are dropped into the 'Alpine Redoubt' area of Austria, where Hitler plans to gather his SS units and make a desperate last stand against the Allies. This is the most heavily-policed area of the Third Reich, swarming with Gestapo. Capture means certain death; and for Fred and the other Jews, it means a horrible death. Yet under Hitler's nose this tiny army blows up trains, steals secrets and even impersonates German officers.
Eventually Mayer is captured and tortured by the Gestapo, but still he does not break. Meanwhile the Allies are approaching, sounding the end for Nazi Germany. Mayer, in his greatest act of chutzpah, convinces his tormentor, the commander of German forces in Innsbruck, to surrender his forces to him, convincing the officer that it would be better to surrender early than risk being shot defending a lost cause.
This is a great World War Two story of derring-do and revenge. And it's never before been told.