Yes this point is driven home in the Group 51 Operations research doc. That within two years the Germans had reduced the entire world wide shipping capacity by 1/5. Since the UK needed 30 million tons per year in peace time , when the world wide capacity was down to 33 million tons, it would soon require that entire world capacity to keep the UK functioning. Apparently 2/3 of the ships being targeted was tankers and the monthly consumption in the UK got to the point where the military functioning was threatened.alecsandros wrote:What matters is the ship tonnage, not the numbers of ships sunk. And more importantly, the cargo of the ship - oil, food, weapons.lwd wrote:If one looks at:
Losses in 39 are almost insignificant ~200 with ~half or less due to U-boats so hardly close in 29
In 40 the numbers go up ~1,000 with again around half due to U-boats and in 41 they increase to ~1,200
It's only in 42 that we see a spike to ~1,600 with 2/3 due to subs but by then US production is making up for over half the losses and produciton exceeds losses after that.
So the only time it could be anywhere close to the edge would be 1940-1942.
The Germans didn't have to sink all the merchants, just enough to stop Britain from being able to carry out the war.
Cheers,
http://ibiblio.org/hyperwar/USN/rep/ASW-51/index.html
http://ibiblio.org/hyperwar/USN/rep/ASW-51/ASW-8.html
I got Mallmanns book on the German decryption code breaking efforts and even though its far from complete, its definitely illuminating.
In late 1940 German Intel knew the location of ½ of the major RN warship flotilla at sea [The rest would be at home ports?] and this was one of the low points, since the RN had just switched their naval cipher code from # 1 to #2. Intercept efforts would fluctuate between decoding ½ to ¼ of all message traffic until naval cipher code # 5 appeared in mid 1943, after that decoding was the exception rather than the rule. The Germans never broke naval cipher # 5. However the German situation was better than this. The British Merchant Navy had their own code cipher was broken and most of their traffic was decoded through out the war until the start of 1943. At this point they had shifted to “Merchant Ship code” and “Special Convoy Cipher”, and B Dienst was only able to decode a small bit of the traffic .
The joint allies made the situation easier with their codes, which allowed ¾ of the transmittions being decoded until late 1943, when the allies introduced a device similar to the German Enigma system. This allowed the Germans to locate most allied convoys general sailing and route through late 1943. However even at this late stage in the game, allied use of airpower over convoys and the surrounding communications that went between convoy and patrol plane , allowed the Germans to triangulate most allied convoys when they were under attack and thus issue reports. These intercept efforts allowed the Germans to get 10-24 hours warning on the departure of any allied convoy.
Unfortunately for the Germans a lot of this translated information was not used but it did give them an ability to find allied convoys despite the appalling lack of Luftwaffe air support the Uboat effort got during the war. Further the improving quality of German hydrophones allowed their Uboats to detect enemy convoys at considerable distance [100-150km] When this was combined with B-Dienst Convoy alerts, it allowed most allied convoys to be intercepted if the Uboats were within 200-400km of the port the Convoy departed from. Even when the allies drove the Germans below the surface, they were still able to get intercepts if they were within ~ 100km of the convoys.