Germany's invasion inflicted great suffering on the people of the Soviet Union, and vengeance was their response. The Soviet leader, Stalin, believed that the German masses had been misled, and he looked forward to the people of Germany eventually embracing Communism, but the spirit of vengeance would not help the Russians win the respect of Germans at the end of the war the way that Americans would win the respect of the Japanese. The rape and plunder of Germans by Soviet troops might have been emotionally satisfying, but it didn't serve the Soviet Union's long term interests. And it added to the tragedy of the most horrendous of wars.
Winston Churchill and President Roosevelt were pursuing what they believed was in the best interest of their nations. Like the Russians they were on the winning side, but it might have been done better. Negotiations between the U.S. and the Soviet Union began in 1942, and they had continued at the Teheran summit conference in 1943. It seems that Roosevelt had illusions in bargaining with Stalin. Roosevelt and Churchill believed that the division and occupation of Germany and the reparations that they agreed to at Yalta in early 1945 was the best they could do given the circumstances that existed on the ground at the time. When the Yalta summit conference began the Soviet Union's Red Army was already in control of much of East Europe and 200 miles from Berlin. It is unfortunate that something better than the Yalta agreements had not been worked out earlier in the war.
Perhaps Britain and the U.S. would have been in a better position to create an end-of-war more to their liking if they had invaded closer to Germany in 1942, as Roosevelt had promised, rather than the landing that year in Morocco and Algeria – which pleased Hitler because he had feared a landing closer to home. In 1942 the Germans were occupied with the Russians. The Battle of Stalingrad began in August, and the Russians were desperate for the British and US to open a Second Front. But, according to historian Max Boot, the invasion of Europe – D-Day, June 6, 1944 – was not possible until "Allied domination of the skies was complete," and that did not happen until 1944. (War Made New, by Max Boot, p 276.)
Perhaps the war would have ended sooner if at the Casablanca conference in 1943 Churchill and Roosevelt had not decided to demand an unconditional surrender from Germany. This declaration was pomposity. War always ends with talk, and conditions are always a subject of discussion.
The German war machine should have been utterly defeated as talks were in progress, and by losing the war Hitler and his National Socialists were doomed politically. The object of the war was to undo Germany's conquests and to have in power in Germany those who would respect international law and agreements. An occupation of Germany was perhaps necessary, but not necessarily the prolonged occupation that occurred. It was no more necessary than a prolonged occupation of that other adversary in Europe: Italy.
Britain and the U.S. had put boots on the ground in Italy. The Italians themselves dealt with Mussollini. In 1943, Italy's king, Emmnuel III, who had supported the fascist dictator Mussolini, ordered Mussolini's arrest and appointed the former fascist party member and conqueror, General Pietro Badoglio, to form a new government. That was the beginning of Italy's emergence from fascism. It was imperfect, but it worked out okay.
The Allied forces (AMGOT) were out of Italy altogether on December 31, 1945. The Allies left much of Italy to manage its own affairs. Where they had remained they had worked in close cooperation with Italian authorities. Where the Allies had tried to apply control over local politics, as in Sicily, they had made a mess of things.
The Italians were aware that they had been defeated militarily. This had discredited Mussolini. It was important that the German people know that they had been defeated militarily and important that Hitler's regime be discredited in the eyes of the German people. This done, we should have left the Germans to govern themselves sooner than we did. The same goes for the Soviet Union, which gained no benefit from the occupation of its zone in Germany for years after Germany's defeat.