[Tallguy]

The German strategy of using heavy warships to disrup sea born supplies was a miserable failure. If the resources were put into more U-Boats the Battle of the Atlantic would have been very different.

I think that what the German Navy was trying to do was force the allies onto the horns of a dilemma: U-boat attacks force the merchant marine into convoys, but the convoys in turn are easy pickings for a heavy surface raider (like Graf Spee). There were attempts to disrupt the arctic convoys from occupied Norway in this manner. The strategy might have worked if the communications between surface and sub-surface raiders had been more effective AND the British not had sufficient battleships to accompany the convoys. Neither was the case, as it turned out.

[Semper Paratus]

I think that what the German Navy was trying to do was force the allies onto the horns of a dilemma:

The German High Seas Navy tried to do what they could do but they knew the correalation of forces vis a vis the British Royal Navy was way against them.

When the US came in they pretty much retired their surface ships.