Kptlt. Adolf Piening, then in command of U-155, invented this Route as a means to escape allied aircraft over the Bay of Biscay in 1943. This route saved many boats during its short life (the Allies forced the neutral Spanish to drive the U-boats out of their territorial waters).
This was a difficult and time-consuming route to undertake but it was preferred by many to the dash through the middle of the Bay. The benefits were that the allied aircraft were at their extreme range on this route but they then moved hunter-killer escort groups to plug the weak spot. U-119 was lost in such a way.