Numerous responses to my OP have misread it, probably strategically. One of the most egregious mis-readings or mis-representation of the OP is to claim that it favors a reduction in merchant shipping or reduced focus on the Battle of the Atlantic.
Rather than address each individually, I'll quote the OP:
TheMarcksPlan wrote: ↑
05 Apr 2020 09:58
[*]Military spending and doctrine favors control of sea communications
, securing air superiority, and cumulative army combat power over strategic bombing and peripheral operations.
All of these posters are missing the fundamental point here: The Wallies spent such a small portion of their armaments production on land warfare that army production can be vastly increased without prejudice to merchant shipping or ASW. In fact, as the OP lays out, spending on merchant shipping (though not necessarily on ASW) would be increased in this ATL.
has posed a number of questions that are very useful for illustrating the common strategic misconceptions that inform most of the responses in this thread:
#2 How to win the naval battle of the Atlantic with less investment in the Navy?
As stated above, there is no less investment in ASW, at least not in the period up to July '42 or so.
A more resolute focus on Europe First and early invasion would have led to earlier victory in the Atlantic. In Jan-June '42 2.83mil tons were sunk off U.S. coastal waters and in the Carribean; this was an entirely preventable disaster as nearly all the sinking were of unescorted ships. Had the U.S. retained sufficient escorts in the Atlantic - even at some marginal cost to the Pacific Fleet - at least 2mil tons of shipping could have been saved. See O'Brien 260-272.
After the '42 shipping crisis, the U.S. and (to a lesser extent) the UK over-invested in escorts. Escort spending increased from $3.3bn planned in April '42 to $4.8bn in December '42. O'Brien 246. Most the delta to escort production was either cancelled later (with associated planning/allocation/partical construction inefficiencies) or entered service long after the crisis had passed.
The extra $1.5bn in escort spending caused by the errors of early '42 (too little U.S. resources devoted convoys) is nearly as much as the U.S. spent on ALL GROUND MUNITIONS
in the second half of '42 ($1.68bil).
#3 How to win the air war over Europe with less investment in the Army Air Corps?
This is a very illustrative misunderstanding.
The poster fails entirely to distinguish different domains of air power. Among these domains are at least (1) local air dominance, (2) tactical air-ground power, (3) operational/interdiction air power [attacks on ground troop movements and communications], and (4) strategic bombing.
Of these domains, the OP specifically proposes cuts to (4) only. I suspect the commenter doesn't appreciate the scale and expense of U.S. strategic bombing effort during WW2.
Invasion of Europe requires air dominance over the landing zone, not some unspecified victory in the "air war over Europe." To achieve air dominance over the landing zone, the Wallies could simply have shifted some of strategic bombing resources into fighter production.
#4 Where to find the merchant shipping to support an Overlord scale operation in 1943?
Two routes: (1) saving ships and (2) building ships.
(1) As discussed above, the U.S. saves >2mil tons of merchant shipping in early '42 by a more resolute focus on Europe and attendant diversion of escorts from the Pacific for Caribbean/coastal convoys. Before getting to (2), let's look at the impact of just those 2mil tons saved. The U.S. Army's study Global Logistics and Strategy (GLS) has some great tables relevant to this discussion:
As you can see from the per-man tonnage requirements, shipping an infantry division required ~94,000 tons in late '42 and ~61,000 in late '43.
Armored divisions required ~3x as much space for all the vehicles.
Average turnaround time of UK-bound cargo ships in '43 was 60 days. GLS '40-43 p.725. Each ship could make, on average, 6 trips per year.
So in the year preceding a Spring '43 invasion, 2mil tons of shipping could have moved 12mil shipping tons or 150 ID's.
Of course that number has to be reduced for non-div. slice deployment. In '45, in-theater division slices were as follows:
Assuming that '43 in-theater slice would be similar to '45, and assuming that the non-div. personnel deployed took as much shipping space as ID personnel, our 2mil tons saved moves ~58 ID's.
While it is true that early-'42 losses were disproportionately oil tankers and bulk (bauxite) fleet, these ships needed replacement in the relevant period and, absent their loss, U.S. shipyards could have built more general carriers while maintaining OTL tanker/bulk capacity.
So we don't even need to build more ships to get 50-60 ID's across the Atlantic if we prevent the early-'42 disaster by focusing on Europe/invasion rather than sending so many ships to the Pacific.
But of course we can also build more ships - merchant shipping construction was only ~8-9% of American expenditure during the war. While there is an early-war bottleneck on shipyard capacity, that bottleneck isn't fixed on a timeline that starts in '40 and there are other avenues such as the construction of concrete ships outside of the normal shipyards. The U.S. built half a million tons of concrete ships as an emergency program early in the war. https://books.google.com/books/about/Su ... YPCLw_u6EC
#1 How the US would gain operational experience with a vastly expanded army in order to avoid a Kasserine Pass on a grand scale?
Kasserine was embarrassing but it's an exaggeration to pretend that the U.S. Army was so bad that the German would have whipped it under any circumstance. Sure there'd be a learning curve in Europe but, just as in North Africa, the weight of numbers of would prevail.
#5 Persuading the British to risk their last army on what they historically considered a highly risky venture?
If the U.S. is committed to invasion the British aren't just going to sit it out. Churchill wasn't thrilled about Overlord either.