In December 1939, the German Army issued its own study paper (designated "Nordwest") and solicited opinions and input from both "Kriegsmarine" and "Luftwaffe". The paper outlined an assault on England's eastern coast between The Wash and the River Thames by troops crossing the North Sea from ports in the Low Countries. It suggested airborne troops as well as seaborne landings of 100,000 infantry in East Anglia, transported by the "Kriegsmarine", which was also to prevent Royal Navy ships from getting through the Channel, while the "Luftwaffe" had to control airspace over the landings. The "Kriegsmarine" response was focused on pointing out the many difficulties to be surmounted if invading England was to be a viable option. It could not envisage taking on the Royal Navy Home Fleet and said it would take a year to organise shipping for the troops. "Reichsmarschall" Hermann Göring, head of the "Luftwaffe", responded with a single-page letter in which he stated, " combined operation having the objective of landing in England must be rejected. It could only be the final act of an already victorious war against Britain as otherwise the preconditions for success of a combined operation would not be met".