according Rick Atkinson "The day of battle", at the end of the Sicily campaign (August 1943), the angloamerican allies had only 25 divisions operational. So I guess that to reach that figure of "63 divisions" they should have to send to the battle badly trained and underequipped divisions.The Western Allies had a total of 63 divisions potentially available for a cross-Channel landing and buildup. The Germans had just 44 divisions in France,

At the same time, in November 1943 the Allies were unable to save the british soldiers in Leros, showing their powerless condition, as Eisenhower admits in "Crusade in Europe" about that episode.

Besides, previous to this invasion of France in summer 1943, the germans would be aware of the preparations so they would have time to send elite armored forces to France (as it happened in 1944). So, probably "Zitadelle" battle in Russian would be aborted and that would have been a very lucky situation for Hitler: angloamerican disaster in France, and not doing the counterproductive Zitadelle offensive in Russia.

Also, an Allied invasion in April, May or June of 1943 would have drawn that new generation of German tanks west to the invasion instead of letting them proceed east to Kurst where they went into action against the Russians in July, 1943.The appearance in Normandy of the new Mark V Panther and the Mark VI Tiger tanks without the Allies having absolutel control of the air would have spelled disaster for an Allied invasion force.

A) what the best strategy for the Western Allies to pursue in terms of defeating Nazi Germany, which was the only one of the three Axis powers that had the scientific, technical, and industrial wherewithawl to threaten the Western Hemisphere. The obvious answer is "Germany First" which both the US and UK had agreed to prior to Pearl Harbor and the German and Italian declarations of war upin the US in December, 1941.

B) Given A, what was the most straightforward way of defeating Nazi Germany; obvious answer, again, is to force the Germans into a multi-front war, ideally in theaters where Allied advantages could be brought to bear.

C) Given B, which theaters are those? Obvious answer, Eastern Front where the Soviets could bring numbers to bear, and – the Americans would argue – the Western Front (ie,. France and the low countries) where Allied seapower could sustain an expeditionary force aimed at Germany's industrial heart, the Ruhr Valley. The British did not disagree, but saw control of the Mediterranean as a necessary interim step to make the maximum use of the Allied shipping pool aand at least open a potential "third front" against Germany that would have to be defended, thus stretching German resources even more.

D) Given A-C above, the question is, how could the Western Allies wage war most efficiently and expeditioulsy against Nazi Germany.

The answer would seem to be to use TORCH in 1942 as a stepping stone to an invasion of NW Europe in 1943, not simply as a "second front" in the Mediterranean. The strategic purposes of TORCH (put the Allies on the offensive in the ETO in 1942, shorten Allied shipping lines around Africa, and bring the French nation actively into the war) could have been accomplished by an enlarged expedition to French North Africa in 1942, one that added Tunisia to the initial targets of Morrocco and Algeria. The forces necessary to have done this (basically, by adding one additional division to the five division equivalents embarked for TORCH historically; this could have been provided by the Allied forces already in the UK at the time of TORCH and by additional US shipping. This would have required cancelling the US offensive into the Solomon Islands (South Pacific Theater) in 1942, which was entireley possible.

That gives the Allies control of French North Africa by the end of 1942, eliminates the Tunisian campaigbn, and leads to the Axis surrender in Africa occuring early in 1943, presumably in Tripolitania (Libya) rather than Tunisa in May.

This basically puts the Allies in the strategic situation they faced in June, 1943, five months earlier – which allows all sorts of possibilities. One possible line is:

BRIMSTONE-FIREBRAND – Allied invasion of Sardinia-Corsica in the spring of 1943;
ROUNDUP (Allied invasion of NW France) in the summer of 1943;
ANVIL (Allied invasion of Southern France) in the fall of 1943.

The above would, essentially, replace the "Mediterranean" strategy as it was enacted, which was:

HUSKY (Allied invasion of Sicily)
BAYTOWN (Allied invasion of Calabria)
AVALANCHE (Allied invasion of Southern Italy)

The end result is the Allies could have been established in strength in France by the summer-fall of 1943, rather than the summer-fall of 1944.

The other points worth remembering is that Axis forces in the West (including Italy) were actually weaker in overall numbers, equipment types and strengths, and training and preparation time in the summer of 1943 than they were in the summer of 1944; in addition, the distance between the Eastern Front and what would have been Germany's Western Front was actually greater in 1943 than it was in 1944, lengthening the amount of time it would take to move a German formation from one front to the other.

All in all, if one really looks at the correlation of forces, the element of risk in an Allied invasion of NW Europe in 1943 is comparable to what it was in 1944.

In esence, from the grand strategy point of view, the Allies could have traded the results of the 1942-43 offensive in the South Pacific Theater (Southern and Central Solomons campaigns), the 1943-44 offensives in the SW Pacific (NE New Guinea, New Britain/New Ireland, and Netherlands New Guinea), the 1943 offensive in the North Pacific Theater (Attu and Kiska operations), the 1942-44 Burma offensives (the "Chindit" operations and the 1942-43 Arakan offensives), and the 1943-45 offensives in the Central Mediterreanean (Sicily in 1943 and Italy in 1943-45) for NW Europe in 1943, for an opportunity to liberate France and Belgium in 1943 and invade Germany in 1944.

All in all (and with hindsight, of course) it seems pretty clear that an opportunity to defeat Germany in 1944 was lost through the decision to invade Italy, rather than France, in 1943.