World War II was the defining event of our age-the climactic clash between democracy and tyranny. It led to revolutions, the demise of empires, a protracted Cold War, and religious strife still not ended. Yet Churchill maintained that it was all avoidable: "If the Allies had resisted Hitler strongly in his early stages...he would have been forced to recoil." Here is a transformative view of Churchill's prescriptions, and the degree to which he pursued them in the decade before the war. It shows he was both right and wrong: right that Hitler could have been stopped; wrong that he did all he could to stop him. Could WW2 have been prevented? Yes-at one juncture in particular-but with great difficulty.