Everybody agrees more anti submarine aircraft were needed, reinforced by the ineffective bombing raids, but how many? With all the information available today if it is not possible to give a well agreed answer what chance someone in 1941? Start with what is the optimal number of aircraft simultaneously patrolling around a convoy and any extra required if within range of enemy bombers, similar for barrier patrols, not only where but how often each area is searched in a given time period. Should there be more patrols at night than day? Part of the answer is it depends on U-boats present, aircraft were the quickest way to help ships under threat, more U-boats in the area, the more aircraft sent, if they were available.
They were doing it, firstly the overall anti submarine effort totals from the Coastal Command Summary. Which gives total hours flown in 1940 as 135,357
| Year | Sorties | Hours | Hr/Sortie |
1939 | 3178 | 12834 | 4.04 |
1940 | 19457 | 78002 | 4.01 |
1941 | 18254 | 95135 | 5.21 |
1942 | 18319 | 129669 | 7.08 |
1943 | 24431 | 222897 | 9.12 |
1944 | 29260 | 272619 | 9.32 |
1945 | 10123 | 92810 | 9.17 |
| Total | 123022 | 903966 | 7.35 |
Next Air 15/789 monthly reports for 1940, hours, Patrol = offensive and security, May 1940 Convoy hours given as 2,830 hours but that makes grand total incorrect, of course the hours flown do not match the summary ones. The allocations are backed up from reports by people like Clay Blair about the safety of convoys
| Month | recon | a/sub | Patrol | Convoy | Other | Total |
Jan-40 | 1863 | 1990 | 0 | 2180 | 465 | 6498 |
Feb-40 | 1572 | 2187 | 0 | 1817 | 509 | 6085 |
Mar-40 | 1818 | 2606 | 172 | 4543 | 531 | 9670 |
Apr-40 | 2740 | 2298 | 427 | 4975 | 750 | 11190 |
May-40 | 2930 | 2553 | 0 | 5830 | 2386 | 13699 |
Jun-40 | 3596 | 2823 | 496 | 6628 | 2475 | 16018 |
Jul-40 | 5121 | 2020 | 454 | 5850 | 1768 | 15213 |
Aug-40 | 3516 | 1363 | 662 | 6700 | 1435 | 13676 |
Sep-40 | 3544 | 1729 | 677 | 5986 | 1851 | 13787 |
Oct-40 | 2606 | 1811 | 459 | 5700 | 1282 | 11858 |
Nov-40 | 2467 | 1468 | 499 | 4316 | 1703 | 10453 |
Dec-40 | 1865 | 839 | 478 | 3064 | 1836 | 8082 |
| Total | 33638 | 23687 | 4324 | 57589 | 16991 | 136229 |
The strategy in 1939 was avoid all out bombing, in 1940 survival, in 1941 more bomb the economy to stop overall production.
Bomber Command. 1939/40 no U-boat bombings from 14,731 tons dropped, the top 10 being Airfields 1,817 tons, Port Areas 1,748 tons Ships, 1,539 tons, Marshalling Yards 1,512 tons, Industrial Areas 1,411, Roads 983 tons, Oil/Synthetic 830 tons, Troops 809 tons, Rail Lines 774 tons, Oil Refineries 677 tons. Not the most strategic air force.
1941 U-boat bombing 72 tons, ship yards 2,042 tons out of 35,548 tons dropped
| BC | UB/Base | UB/Pens | UB/Slips | UB/Yards | UB/Yards & City | Total |
1942 | 0 | 0 | 63 | 1166 | 294 | 1524 |
1943 | 0 | 324 | 0 | 0 | 0 | 324 |
1944 | 85 | 2578 | 0 | 0 | 0 | 2663 |
1945 | 0 | 393 | 0 | 10304 | 0 | 10697 |
| Total | 85 | 3295 | 63 | 11470 | 294 | 15207 |
8th Air Force. All bomb data in short tons, rounded to nearest ton, entrance = lock gates and port area.
| 8th AF | UB/Base | UB/entrance | UB/Facilities | UB/Pens | UB/Yards | Total |
1942 | 0 | 0 | 0 | 8 | 0 | 8 |
1943 | 0 | 301 | 81 | 1609 | 4335 | 6325 |
1944 | 314 | 0 | 0 | 0 | 4393 | 4707 |
1945 | 0 | 0 | 0 | 0 | 8298 | 8298 |
| Total | 314 | 301 | 81 | 2111 | 17025 | 19832 |
Both rather end loaded, the 8th dropped 2,859 short tons on U-boat targets in January and February 1944, then none March to June inclusive.
One of the things to remember is how few U-boats were available for the first two years of the war, their abilities and the circumstances made them very efficient, to be repeated in 1942 off the Americas it means there were not a lot of U-boats passing through the barrier patrol areas and they generally transited the northern one only on their first patrol. Then comes selling barrier patrol success in U-boats not spotted as they had to stay submerged. At least daylight only convoy patrols could force U-boats to break contact even with slow convoys. Barrier patrols needed radar equipped aircraft to become really effective, into 1941 and even later the number of radar sets, their weight and drag limited the suitable aircraft, as does the need for lights for night attacks. Radar carrying aircraft around convoys completes their protection.
All the above would be enhanced if the aircraft and ships could quickly talk to each other. Forming more convoys earlier required the understanding weakly protected convoys were usually better than independent sailings. More aircraft would encourage more convoys.
So how many aircraft? Of what types? How does this vary according to number of U-boats, convoys and threats from air attack? How about flexibility, quickly moving bases according to threats, what advantage several Coastal Command Squadrons moving to the US in early 1942, pairing with similar USAAF/USN units and doing patrols.
Things like Operation Torch, troop movements and Arctic convoys all drew escorts away from the trade convoys, so what allowance for these generally increasingly larger operations?
The UK Statistical Digest notes by value UK imports went up during the war, exports halved. When it comes to tonnages the disruption of trade routes needs to be taken into account.
imports "declined from a prewar average of more than 50 million deadweight tons to 42 million in 1940 and 31 million in 1941. In 1942, despite desperate efforts to arrest the decline and increased assistance from the United States, they fell to 23 million."
British War Economy, page 432
"How near did the United Kingdom really come to the point of danger, where supplies of food and raw materials would have been inadequate to feed the population and keep the war factories working, unless shipping had been quickly diverted from military operations? It will not be possible to give a convincing answer to this question until more research has been done; but some evidence which is already available suggests that the country was not quite so close to the margin of danger as the War Cabinet at that time believed. The estimates of minimum import requirements on which the War Cabinet based its policy were themselves based on calculations of minimum stock levels and the rate of consumption of imported commodities. Looking back, it would seem that the calculations under both heads were too sombre. For example, in the first report of the Shipping Committee, the net consumption in 1942 of importable food was put at 12.4 million tons and of raw materials at 15.1 million tons; but in fact, the actual realised figures were 11.4 million tons for food and 13.3 million tons for materials. Similar discrepancies occurred between the forecasts and the statistical facts for the later war years. In the estimates for food there was perhaps considerable justification for a fair margin of error, since the Ministry of Food had always to allow for the vagaries of the weather and the possibility of bad home harvest. There was less justification for the erroneous estimates of raw material consumption; indeed, the inaccuracies of the Ministry of Production's forecasts serve as a reminder of the limitations of wartime planning even in its later stages.
These overestimates of consumption managed that the United Kingdom managed quite well in 1942 and the early months of 1943 with a volume of imports lower than the stipulated minimum. If it should also be proved that the estimates of minimum stock levels were in some degree inflated, the conclusion would be that the British could in this period have maintained an unimpaired war effort at an even lower level of imports: alternatively, that they could have gone on longer than the Government believed at the low rate of imports actually achieved. To some extent, the estimates of consumption hang together; if the former were inflated, then it followed that minimum stock levels, calculated on the basis of so many weeks' supply, were also overestimated."
Britain did not come as close to danger as thought so at the time, the safety margins were thinning out to where a bad year for agriculture would create major problems. Arable land had gone from 12 million to 17.4 million acres, the 1943 wheat crop was 3,435,000 tons, but the 1945 one was 2,174,000 tons. While 1,705,000 tons of US food arrived in 1943. For a series of 15 main food stuffs (Wheat, Barley, Oats, Mixed corn, Rye (grain), Potatoes, Sugar beet, Beans, Peas, Turnips and swedes, Mangolds, Hops, Mustard (seed), Fruit, Vegetables) Britain increased output from the per war average of 28,500,000 tons to 42,546,000 tons in 1943 but down to 40,759,000 tons in 1944 and 40,473,000 tons in 1945. In Great Britain the cattle herd went up by 10%, Sheep down 25%, pigs and poultry down 50% each, fish consumption per capita halved until late in the war. In 1942/43 Britain was relying on reasonable growing seasons in Britain.
The RN started WWII with a nominal strength of 107 new, 79 old destroyers and 32 sea/ocean going anti submarine ships, total 218 plus the French fleet. In December 1940 it was 90 new, 71 old, 50 ex US and 18 Hunt class destroyers, plus 64 escorts, total 247, the building program kicked delivered in 1941 so December strength was 88 new, 66 old, 47 ex US and 44 Hunt class destroyers, plus 224 escorts, total 471. Figures include those under repair, refit etc. Losses to the above ships were 3 in 1939, 42 in 1940 and 33 in 1941, including 48 modern destroyers, it took until July 1943 before the modern destroyer strength regained its September 1939 figure.
By end 1942 the above categories had 503 ships, end 1943 it was 685 ships, end 1944 it was 818. Escort carrier strength as of December 1941 to 1944 were 1, 7, 35, 40.
The battle fleet started with 15 battleships, 6 carriers and 64 cruisers, end 1944 it was 14 battleships (including several in reserve), 9 carriers and 60 cruisers (including those in reserve). This excludes Free French, Dutch, Greek etc. ships under RN control but not RN ships manned by allies.
German passive sonar was better than allied and could usually detect ships beyond U-boat visible horizon, with limitations on bearings.
