Usually, just for the sake of form, the Allies send out a search plane beforehand to pretend to stumble upon the milchcow. But, setting aside some of their blind spots in the political realm, the Germans are bright chaps, and cannot be expected to fall for that ruse forever. If we are going to keep sending their milchcows to the bottom, we need to come up with a respectable excuse for the fact that we always know exactly where they are!