While the Big Three and their continental Allies fought against Nazi Germany, another war was under way on the continent: the war to shape the political landscape of post-war Europe. In the Balkans, the war overlapped with political and ethnic conflicts, engulfing the region in bloody civil wars. In Central and Eastern Europe, partisan movements engaged the Germans without losing sight of the danger posed by the arrival of the Red Army. In France and in Italy, the adoption of the slogans of national liberation provided the communist parties with a formidable democratic legitimacy, which established them as key players in the political lives of their countries.The British and the Americans worked to stir up, support, control, and direct these resistance groups. London created the Special Operations Executive (SOE) and Washington the Office of Strategic Services (OSS), both of whom sent agents into occupied Europe to liaise directly with the guerilla groups. Through the Comintern, Moscow carefully coordinated the actions of the European communist parties with the foreign policy of the Soviet Union, which was acting for the first time as a key player in the arena of international relations. The forests and the mountains where the partisans were fighting the Germans soon became a major part of the proxy war that the Big Three waged to shift the post-war geopolitical balance in their favour. Looking for the first time at the Big Three in a comparative study and spanning Europe from Yugoslavia to Poland, from Greece to France and Italy, this book vividly depicts and sharply analyses how this proxy war shaped the history of the post-war settlement. In so doing, Piffer deftly connects high political histories with history from below, making the book important reading for all those interested in the history of the war and cold war, communism and Resistance, and diplomacy and intelligence.