Black cross - Greg Iles (World War Two #1)

In January 1944, four people hold the fate of the world in their hands. They are not statesmen or generals, but an American doctor, a German nurse, a Zionist killer, and a young Jewish widow. These four are brought together in a place almost beyond imagination: a small SS-run concentration camp harboring a weapon so lethal that it could wipe out an entire D-Day invasion force.

What they are forced to do in the name of victory—and survival—shows with terrible clarity that in a world where all is at stake, war can have no rules.