Lone Wulf by Noah Harris

March 1945. American GI Gene Fuller has nearly died in a dozen horrible ways and has watched what happens to friends who aren’t so lucky. But now, in the war’s final weeks, he’s more scared than ever. Guarding a rear area, his regiment comes under attack by the Werewolves, a fanatical band of Nazi diehards who brutally slaughter any American who falls into their hands. Private Fuller has to rely on his wits, his lovers in the regiment, and a mysterious and handsome German prisoner in order to survive. That may not be enough.