Furubotn kept a low profile during the first couple of months of the occupation, but was soon busy preparing resistance work across party lines and inspite of party policy. The fact that he did not openly criticise the party line has led some former politicians and opponents of Furubotn to maintain that in 1940 he adhered to official NKP policy.(107) But it was not Furubotn's style to oppose the party openly; to do so would have run counter to what his many years of experience of Communism had taught him. His opposition tended to be hidden and tactical, the sort of thing Arvid G. Hansen had in mind in 1925, when he spoke of systematic opposition which consisted of keeping criticism to oneself, while at the same time confronting the organisation with ``faits accomplis''.

There is plenty of convincing written and oral evidence to show that Furubotn was a pioneer of Norwegian and European resistance work. In the summer of 1940 he was already proposing to the NKP Central Committee that the leading party officers should go under cover, although the party was still legal. Arne Pettersen, who was at the meeting, says the proposal was defeated only by a narrow majority – it should be noted that in 1949, Pettersen was one of Furubotn's main opponents in the party. When the Germans started looking for him on 16 August 1940, Furubotn was the only Norwegian politician they were trying to lay their hands on. The first ``Wanted'' notice appeared in Norsk Politidende (Norwegian police news) on 24 August, followed by others on 10 December 1940 and 25 February 1941 - at which date he was still the only politician listed. By then he had already been in hiding for half a year, unlike his fellow centrally placed party-members in Oslo. He had a number of narrow escapes from the Gestapo. The immediate occasion of his opting for illegal activities in August 1940 was that the Germans banned the NKP on 16 August, and kept its main leaders under arrest for some days. The NKP was the first party the Germans banned.

During the autumn of 1940, Furubotn began bombarding the central leadership in Oslo with communications, excoriating those party members who were cooperating with the Germans along the lines laid down by the group which called itself Fagopposisjonen av 1940 (the trade union opposition of 1940).(108) They were a gathering of oppositional left-wingers from within and outside the Labour and Communist parties who harboured illusions about safeguarding a minimum of Norwegian interests and freedom of action by adapting to the demands of the occupying power. Furubotn wrote on 8^th October 1940 that this opposition had drawn up a political line which was a ``horrifying example of a policy which cannot be ours....The opposite must be the case''.(109) The opposite was resistance, and that was what Furubotn was already organising in Western Norway. Although Furubotn did not make his criticism of the party public or official, but sent it in personal letters to the NKP leader Henry W. Kristiansen in Oslo, a reaction to his challenge had to come sooner or later. In the winter of 1940-41, the central leadership tried to have him removed as party secretary for Western Norway.(110) The move was dangerous to Furubotn. A former NKP leader and editor of the Bergen Communist newspaper Arbeidet (work) declared himself the rightful Secretary. While keeping one step ahead of the Gestapo, Furubotn was now also faced with having to secure his political platform within the party. A factor which made the attack especially difficult to deal with was that the old NKP Committee for Western Norway was by then in a concentration camp, and without their support Furubotn's political future would have been in great jeopardy. However, he succeeded in making contact with them by letter, and won support for the policy he was fighting for. When this became clear in the spring of 194l,(111) the NKP leadership in Oslo resumed the contacts with him which had been broken off for about half a year.(112) They sent word that they were engaged in working out a political platform similar to the one he had adopted in Western Norway. It is difficult to say what lay behind the change of tack in Oslo but by all accounts a conflict with Furubotn would have been difficult for the tiny Oslo NKP group to sustain. He had the support of the party leadership in Western Norway, which was after all the NKP's largest district.