Germans Build Submarines Instead of Warships?
Let's say that starting before the Nazi take-over, maybe 1930 or 1931, key figures in the German navy become convinced that U-boats rather than battleships are the future of naval warfare. They do studies of contemporary designs and do paper designs of their own, then when Hitler comes to power, convince him that submarines would give Germany a way to leapfrog the navies of their potential enemies. As a result, instead of building destroyers, cruisers, battlecruisers and then battleships, the Germans build more and larger submarines. As the silent service, the U-boat only navy seeks to remain secret. Surfacing only at night. Building within secure assembly sheds. Docking in underground pens.
reference:
http://www.uboat.net/
U-boat production:
Year (OTL) ATL
1933 (0) 8
1934 (0) 16
1935 (14) 16
1936 (21) 20
1937 (1) 40
1938 (9) 40
1939 (18) 60 200
1940 (50) 200
1941^ (199) 250
1942~ (237) 300
1943* (284) 350
1944 (229) 300
1945 (91) 120
Total: (1153) 1720
^ radar detection fitted~ Ju 290 long range naval bomber starts production*Snorkel fitted
Historically, the Germans had 63 U-boats, some light ships, one partially completed carrier and two battlecruisers by the time the war began. Figure that in this scenario they have no surface fleet to speak of and 200 U-boats. Double that in a years time. Since they regard U-boats as a serious threat they have quite a few destroyers to protect Baltic and coastal trade. These might be enough to conduct an invasion of Norway as OTL.
Problems: (1)The Navy historically was reluctant to allow the U-boat arm to have carte blanche, in spite of noted success in the previous war.
(2) It takes a while to get a good submarine design. The first three years production (40) will only be fit for training vessels.
(3) A different German fleet would presumably mean a somewhat different British fleet at start of war. How secret could they keep the U-boat navy? If they succeed might tensions with Britain be markedly lower?
(4) The Germans would have to develop the ancillary equipment to make the U-boats worthwhile, including effective replenishment at sea.
(5) Ultra
So how would this play out?
Would this hurt or help the Germans?