How would a German invasion of Iceland alongside the invasion of Poland affect the Battle of the Atlantic?
Short answerIt would open with a British counter-invasion and probably cost Germany the surface ships sent to support an isolated, unsustainable garrison.
NotesNews of the landing would spread immediately, allowing British warships to converge before Germany could build a sustainable position. Any available pocket battleships or Scharnhorst-class units committed to covering the operation would be far from support, with too few submarines to protect the route, while Britain would gain both the reason and opportunity to retake and occupy Iceland.