At the war's end, many figures in the governments of the Western Allies sought to severely punish Germany for the War. This is best displayed in the "Morgenthau Plan," named after the US Secretary of Treasury Henry Morgenthau Jr. The Morgethau Plan essentially called for the near-complete deindustrialization of Germany. Now, despite its fame, the Morgenthau Plan was not actually adopted as an Occupational policy in any formal sense, but its influence was seen in the mindset of the Western Allies during their occupation of Germany.

German steel production was slashed dramatically, German factories were dismantled and shipped out of Germany as a form of reparations, the price of German coal was set at half of the cost of production, and German civilians were used as forced laborers. Germany had ended the war with an industrial system that was actually fairly intact, despite Allied bombing campaigns, though it was naturally quite low on resources. Most of the destruction of German industry occurred post-1945. In the US zone, Joint Chiefs of Staff order 1067 was in place, an order that specified that the occupiers would "take no steps looking toward the economic rehabilitation of Germany."

What changed the mindsets of the Western Allies, especially that of the US (who, while only one of three Western occupiers in Germany, had a large informal influence over British and French policy), was the myriad of security issues that stemmed from these policies. Even a partial Morgenthau Plan was too utterly destructive to be sustainable in Germany. In 1946, former US President Herbert Hoover toured Germany at the behest of President Truman, and he issued a report stating that "There is the illusion that the New Germany left after the annexations can be reduced to a "pastoral state". It cannot be done unless we exterminate or move 25,000,000 people out of it." Hoover was essentially correct - Germany could simply not feed itself. The destruction of the German economy meant that Germans couldn't afford to import food, and the level of calories consumed by the average German citizen plummeted dramatically.

There had always been detractors of the Morgenthau-style punitive occupational policies in Germany, and the fact that the German people were bordering on starvation helped give credence to their criticisms. The US was spending large amounts of money simply in order to feed the German people, and the destitute state of Germany was slowing the economic recovery of Europe. There were also fears that plagues would ravish Europe as a result of the poor living conditions of its people. What really was significant, however, was the security risk posed by all of this - there was a real worry that the German people might turn to communism. As the General Lucius Clay, the deputy military governor of the US zone in Germany, stated, "There is no choice between being a communist on 1,500 calories a day and a believer in democracy on a thousand." JCS 1067 was overturned in 1947 on the grounds of national security, leading to a gradual process of rebuilding Germany's economy. Western leaders had realized that if Western Europe in general and Germany in particular was to resist communism, the economy would have to have enough of a rate of growth to make the status quo seem like a good alternative. Communist parties were making a fair bit of electoral headway in Western Europe, after all.

I'd say that this argument was quite succesful, in that in a few years the Germans went from being seen as an enemy that needed to be punished to allies against the spread of Communism. As the USSR looked to be more and more of a belligerent power, the idea that the keeping Germany down at all costs seemed a bit silly.

I was just reading Lawrence Kaplan's NATO Before the Korean War, where he discusses the pro/anti viewpoints quite well, and how it differed from the quicker acceptance of Italy after the war.

The switch happened in large part due to creation of both NATO and the WU (Western Union, later Western European Union) on one side, and increasing aggression from the USSR.

In 1949, Germany was still very much an issue the US, Britain and France. eighthgear pointed out the ethical and practical realities that made starving or destroying the German state impossible, but that did not allay all of France's fears. While the North Atlantic Treaty was signed in 1949, "frontline" countries such as France, Belgium and the Netherlands very much felt that, in the case of a war, the best they could hope for is a repeat of WWII, where they soldiers and cities would be massacred while British and American armies gathered. The US and Britain saw that Germany was not just a solution, but an inevitability as an active member of the military Alliance.

Concurrent with this was increased continental integration on the European continent that the US strongly supported in order to rebuild the destroyed western nations. France, besides their historical apprehension for Germany, also fear in a practical sense being tied close to the Germans. They wanted British integration into Europe so France/UK might eventually act as a bulwark to a renewed Germany. But at the same time, the UK was reluctant to join any continental integration, preferring their connection the commonwealth and the US.

So, France reacted strongly against German integration and armament unless the British played a closer role. The British realized that unless Germany was brought into the fold, it would be lost the Soviet, but they did not want European integration. The US pressured the Brits, and the French, but were in an awkward position, as they were keenly sensitive to the Communist claims that the US was imposing its will on sovereign nations.

But with the USSR's recent Atomic and Hydrogen bomb testing, their coup in Czechoslovakia and the raising of an East German "militia" in the fall 1949 which threatened West Germany, softened the French view on German. Over time, connections formed through the ECSC and other organizations and led to Germany becoming an integral member of the western alliance.