Night and Fog — Gregory St. Germain

Scott Gideon left a peaceful America to fight fascists in Spain. That fight was lost-and all Gideon was left with were the martial skills he had mastered, and a burning hatred for fascism.
Now the Nazis were overrunning europe, and Gideon couldn't wait for America to get involved-especially when a Belgian millionaire named Philaix asked him to head a handpicked strike force to wage secret war against the German juggernaut. The money was too good and the vengeance was too sweet. And Gideon led his international killing crew into the heart of occupied Poland to turn the tide of terror and give the Nazi conquerors a taste of their own blood...