I found this great site today that lists all 1153 U-boats built by the Kriegsmarine in WWII. It has details of their war patrols and commander for each boat. Very interesting site and great for wasting a few hours. http://uboat.net/index.html
The U-boats were very effective in disrupting Allied shipping lanes. The Germans maximized their use as much as they could, but in the end, Allied anti-submarine technology became efficient enough to counter them. The Germans were extremely efficient warriors. Their only weakness was their idiot leader. 🙂
I seriously doubt that the Germans could have maintained their European empire even without Hitler. The German military was efficient, yes, but they could not have won the war. It was a matter of when the Allies would win, not if.
Well what if the Germans utilized the Ukrainians as allies against Russia? That might have been enough to topple the Soviets and free up the German resources in the West. The war would have lasted a lot longer that's for sure.
The question is, given that counter-factual, would the Ukrainians have been any more effective militarily than say the Romanians or Italians? Both German allies were more millstones around the necks of the Germans than they were helps. The Italians in particular caused the Germans to spread their strategic focus so wide that the Germans essentially had no focus. Both nations were also fairly ineffective militarily, they were only good for use on quiet sectors of the front and as they demonstrated in the winter of 1942-43 outside Stalingrad they were thin reeds that would break at the slightest pressure. I am not sure that masses of untrained Ukrainians would have been any better. The only good thing that would have come out of German support for Ukrainian independence is a lack of partisan actiivity which would have freed up something like 10 division equivalents for use at the front.