The events of April to June 1940 overturned the balance of naval and air power, as the Germans conquered Denmark, Norway, The Netherlands, Belgium and France. The occupation of these countries permitted the "Luftwaffe" and "Kriegsmarine" to operate from French ports on the Atlantic coast, hundreds of miles closer to the Atlantic shipping lanes. German medium bombers could also reach British ports on the westernmost and northernmost coasts. The advantage enjoyed by the Germans, allowed them to interdict merchant shipping supplying food and war materials to Britain much more effectively, which had the potential to starve Britain. While merchant shipping was suffering these losses, Coastal Command had proven ineffective at countering German air and sea attacks on shipping. But the command could not protect English Channel convoys, and was forced to abandon operations until July 1940. RAF Fighter Command was given the task, supplying air attack and defence with the enemy. Warning signs after the First World War, that U-boats could become a serious threat once again, meant that aircraft would be the best counter to their operations. This fact not being fully understood, Coastal Command became the "Cinderella service" until about 1943.