With North Africa at last free of Axis troops, the Allies pondered where to strike next. In January 1943, while the fighting was still going on, a plethora of American and British dignitaries, led by President Roosevelt and Winston Churchill, attended the Casablanca Conference to find an answer to this question. The American delegation was adamant that the quickest way end the war was to invade France and advance into Germany. France was where the decisive battle would have to be fought, and they pushed for an invasion to be undertaken in 1943. As the Conference wore on, it became apparent to both sides that, given their unpreparedness and the formidable German defences along the so-called "Atlantic Wall", such an operation would not be possible until 1944.
The question, therefore, was what to do in the meantime. The logical answer would have been to prepare the way for an invasion of France by assembling armies in Britain whilst simultaneously reducing Germany's war industry and coastal defences through a sustained bombing campaign. This indeed came to pass, but since June 1940, the Russians had been almost single-handedly bearing the brunt of Germany's military might and the Western Allies were coming under great pressure to relieve the strain on them by opening a second front. With no other tangible means of obliging them in the short term, even those who were wholly against the idea reluctantly began to acknowledge the need for a major offensive in Southern Europe.
The Americans saw little of significance in the Mediterranean theatre, believing it to be a sideshow to the main campaign that was to be opened in France; General Marshall, the US Chief of Staff, went further with his misgivings, "I think the Mediterranean is a kind of dark hole into which one enters at one's peril." In contrast, Churchill had long favoured a major action in the Mediterranean, especially the Balkans, famously describing it as "the soft underbelly of the crocodile". The interests of the British Empire were heavily involved in the region, and they had come to Casablanca determined to win their argument.
As with previous military adventures that Churchill had masterminded in the First and Second World Wars, the ill-fated Gallipoli and Norwegian campaigns respectively, the rewards of success seemed great indeed. In the first instance, Sicily was a base for enemy aircraft and shipping which posed a constant threat to Allied dominance of the Mediterranean. This was a major issue because any merchant ships travelling between the Atlantic and the Far East could not use the Mediterranean but were instead forced to go very much the long way around, via South Africa. Removing Sicily from the equation would make these routes a good deal safer for both military and civilian traffic. Furthermore, the Italian people had never had much enthusiasm for the war, and the disasters that had overtaken their soldiers in Africa and Russia had badly shaken their resolve. Churchill correctly predicted that an Allied invasion of Sicily would so threaten the mainland that Mussolini's government would collapse and with it an Axis power would be knocked out of the war.
Yet this was only the beginning. With Italy out of the way and Hitler's southern flank consequently in disarray, Germany would be left perilously exposed if an Anglo-American force raced up the spine of Italy and spilled out into Central Europe. The British were convinced that such an exploitation of Italy's surrender would considerably shorten the war, and it would, at the very least, remove a great deal of pressure from the shoulders of the Red Army. Moreover, cynical of Russia's post-war intentions, if this force could conquer great swathes of territory, this would naturally form a barrier to keep the communists as far out of Europe as possible.
A little persuaded by this argument and lacking any credible alternative, the Americans reluctantly agreed to support a Mediterranean Campaign. Even so it was made clear that their support was confined to merely testing the water. Sicily would be invaded, but if resistance proved too strong then they reserved the right to abandon a subsequent invasion of Italy in favour of other key Mediterranean objectives, such as Sardinia or Greece. The Americans still considered this crusade against Italy to be nothing more than a distraction from the main campaign that would be launched in France during the following year, and they were adamant that no men or materiel would be diverted from that theatre to support the war in the Mediterranean. It was not a good omen for success.