Hi John, you have set yourself a enormous undertaking, one I am not sure can be answered with any confidence, even with extensive research in the U-Boat Archives in Germany. There are so many variables regarding U-boat commanders and their careers. Such as when they trained, what type of boat they were given, where they were designated to operate and especially at what period of the war they entered service.

In the beginning with few U-boats available U-boat command had the luxury of a pre war training programme, where only the one's that excelled were initially accepted, however after 1939 and especially after 1942-43 when the losses began to mount, time for training and selection became a major problem, both for commanders but also crews. Those crews lucky enough to survive more than a few patrols were in many cases spread out to other boats to give them some experienced men to assist the new crews.

This was only ever going to be a stop gap however as the war went away from Germany, the time for training new commanders and crews became ever more harder as the allied bombing of U-boat building yards, mining of the Baltic training areas all eventually took there toll on the operational performance of each new boat.

You mention the commanders competency, there are some issues of individual's performance, a few were found to be lacking and dealt with by BdU accordingly, however for the most they did their job as best as the deteriorating conditions allowed, much easily up to 1941-42 when anti submarine allied naval and especially aircraft were ineffective. Later as the war progressed the commanders had survival more and more in mind, only striking as any favourable conditions arose.

A few top aces from the early years who were deemed suitable were rewarded later in the war with shore posting command of U-Flotilla's, but again this was always going to end one way no matter how hard they tried.

From my own experience, I took time to look at the U-boat war, and then after dividing the many aspects of it, until deciding on what I wanted to research did I then start. As a coincidence I am currently looking at U-boats that only sailed on one war patrol 1939-45, 258 found so far, of which 204 were sunk and a total of 169 commanders died on the patrol.

Good luck in what you decide to choose. John