I was wondering why the Allied navy were unable to counter the German withdrawal historically.
According to Wikipedia:
The German and Italian evacuation schemes proved highly successful. The Allies were not able to prevent the orderly withdrawal nor effectively interfere with transports across the Strait of Messina. The narrow straits were protected by 120 heavy and 112 light anti-aircraft guns. The resulting overlapping gunfire from both sides of the strait was described by Allied pilots as worse than the Ruhr, making daylight air attacks highly hazardous and generally unsuccessful. Night attacks were less hazardous and there were times when air attack was able to delay and even suspend traffic across the straits but when daylight returned, the Axis were able to clear the backlog from the previous night. Nor was naval interdiction any more practicable. The straits varied from 2–6 miles (3.2–9.7 km) wide and were covered by artillery up to 24 centimeters (9.4 in) in caliber. This, combined with the hazards of a 6 knots (11 km/h; 6.9 mph) current, made risking warships unjustifiable and fear that Italian warships were preparing to attack the Straits of Messina in a suicide run.
(source: Molony, Brigadier C. J. C.; Flynn, Captain F.C. (RN); Davies, Major-General H. L. & Gleave, Group Captain T. P. (2004) [1st. pub. HMSO: 1973], Butler, Sir James, ed., The Mediterranean and Middle East: The Campaign in Sicily 1943 and The Campaign in Italy 3 September 1943 to 31 March 1944, History of the Second World War, United Kingdom Military Series, V, Uckfield, UK: Naval & Military Press, ISBN 1-84574-069-6).
That was my understanding too...although there was also a fair degree of Allied disorganisation and complacency which meant the RN and other allied ships only started trying to block the straits when the evacuation was almost complete. In fact I have moved my ships anyway this turn as I am concerned about the risk of bombardment from both the Italian mainland and Messina from the large numbers of Italian heavy guns Larry still has.
The main effort against the evacuation will have to fall to the airforce I think.
I have to say the chances of a suicidal attack by the Italian navy as described above seem fanciful given the wavering commitment of the Italian armed forces by this time in the war.
"I do not agree with what you say, but I shall defend to the death your right to say it"