The Volokh Conspiracy argues that the USSR saved the largest number of its Jews during World War II -
"The USSR saved its Jews not through decency, love of justice, belief in equality, or any action focused on Jews as Jews. It saved them by successfully resisting the Nazis -- by fighting (often brutally) a brutal enemy, and losing 15% of its population, Jewish and non-Jewish, in the process. It's no shame that the Netherlands or Greece didn't do this; they couldn't. My family, though, is alive -- I am alive -- largely because the Russians could resist, and did."