On 14 December 1939, Quisling met Hitler. The German leader promised to respond to any British invasion of Norway (Plan R 4), perhaps pre-emptively, with a German counter-invasion, but found Quisling's plans for both a Norwegian coup and an Anglo-German peace unduly optimistic. Nonetheless, Quisling would still receive funds to bolster "Nasjonal Samling." The two men met again four days later, and afterwards Quisling wrote a memorandum that explicitly told Hitler that he did not consider himself a National Socialist. As German machinations continued, Quisling was intentionally kept in the dark. He was also incapacitated by a severe bout of illness, probably nephritis in both kidneys, for which he refused hospitalisation. Though he returned to work on 13 March 1940, he remained ill for several weeks. In the meantime, the Altmark incident complicated Norway's efforts to maintain its neutrality. Hitler himself remained in two minds over whether an occupation of Norway should require an invitation from the Norwegian government. Finally, Quisling received his summons on 31 March, and reluctantly travelled to Copenhagen to meet with Nazi intelligence officers who asked him for information on Norwegian defences and defence protocols. He returned to Norway on 6 April and, on 8 April, the British Operation Wilfred commenced, bringing Norway into the war. With Allied forces in Norway, Quisling expected a characteristically swift German response.