Both sides had serious difficulties in the early years, brought about mostly by a lack of resources for DKM, and for RN, a lack of escorts, near criminal shortages of suitable escorts, non existent command structure to deal with uboats early on. Tactics and training on the allied side were woeful. a good example of this was the formation of so-called "hunter killer" groups caused some rather spectacular losses early on, most notably the loss of the Courageous.
As far as air power was concerned, it provided virtually no benefit to the ASW efforts until the latter part of 1940, and then only to a very limited extent. The code breaking efforts from June to December 1941 were a significant step forward, but for the whole of 1942, the escorts were again blinded when the enigma codes were changed again. The development of an effective airborne ASW weapon was badly delayed until late in 1941, and proper fleet co-operation between CC and escort command lagged badly until well after the happy time. Even under the most appalling losses at sea, the RAF with its focus on winning the war by bombing alone was very reluctant to hand over any suitable long range and very long range aircraft to help out. Only when directly ordered to do so did they transfer significant resources to this operational area.
On the German side the glaring weakness was a shortage of training boats. there were just 4 b oats engaged in training in September, with another 4 in work up with a total of 57 in service. By January 1940, with a total of 56 in service, 12 boats were allocated to their training commands and a further 13 were working up. this situation remained more or less the same for most of 1940, which despite the runaway success in the North sea and the Western Approaches (both within range from the german bases) really should be called the year of lost opportunities for the Uboats. New commissionings remained at a trickle, and the allies finally began to get themselves decently organised.
From early 1941 the BDU really started to receive decent resource levels. In the first quarter , the average uboat availability began to ramp up, from an average of 89 at the beginning of the year to 198 by the end of the year. their training resources also grew during this period, from about 11 boats at the beginning of the year (not including work ups) to nearly 60 boats in December.
Another aspect of the Germans effort was the abysmal performance of their torpedoes early on. They wanted to utilise their new magnetic exploders, but these were hopelessly unreliable and caused many unnecessary failures. Another shortcoming lay with the LW. There were no specialised minelaying units, and at the beginning no magnetic mines suited to air dropping. In the whole of DKM the magnetic mine stocks was just 1500, a hopeless reserve given the potential of this weapon. There were no specially designed minelaying u-boats, despite a design having been ready for nearly two years. a sustained minelaying campaign would have been a far more dangerous proposition as it would not have evoked any prewar response from the british like increased U-boat production would have.