Sicily was chosen as the target at Casablanca in January 1943. It was the largest operation the Western Allies had yet planned, involving approximately 160,000 troops, 3,000 ships, and more than 4,000 aircraft from the United States, Britain, Canada, and associated Allied forces.
The problem was visibility. Sicily was the obvious target. The island sat directly north of Tunisia. Its capture would open the entire Mediterranean to Allied shipping, a goal so transparent that Axis planners, British intelligence feared, had drawn the same conclusion. If German and Italian commanders concentrated their defenses on Sicily, the invasion would cost far more than it should, and might fail.
German and Italian forces in the Mediterranean in early 1943 were distributed across multiple points: Italy itself, the islands of Sardinia and Corsica, the Greek mainland and Greek islands, the Dodecanese, and Sicily. Every German or Italian division deployed elsewhere was a division not defending the actual target.
The Allied deception effort was therefore aimed at a specific, achievable objective. It did not need to make the Germans believe that no Mediterranean invasion was coming. Evidence of invasion preparations was too widespread and too obvious to be concealed. What was needed was ambiguity about the specific destination, sufficient to justify the distribution of German forces across multiple possible targets rather than concentrated on the actual one.
In this context, Operation Mincemeat was a tool designed to tip a balance. If German intelligence had a compelling reason to believe that Greece and Sardinia were the primary targets, with Sicily as a secondary one or a deliberate feint, German commanders would hedge their bets. Troops would be spread. Reinforcements would be positioned for the wrong coasts.