The Battle of the Atlantic was sheer war of attrition and tonnage. The Allies were pouring far more in at the top by 43, with the expectation that some would ge

The Battle of the Atlantic was sheer war of attrition and tonnage. The Allies were pouring far more in at the top by 43, with the expectation that some would get through. The strength of numbers of the long range Sunderland 5s - that started replacing the III in 44, Beaufighters, and Mossies meant they were far more effective, particularly out in Biscay. German effectiveness declined really only from 44 on - there was a pretty major and effective U boat campaign in late 43 going into the winter. It just wasn't as effective as the previous year.