Here we have Churchill reading the conclusion of the Chapter XXXVI - Frustation in Norway.
"Twilight War ended with Hitler's assault in Norway. It broke into the glare of the most fearful military explosion so far know to man. I have described the trance in which for eight months France and Britain had been held while all the world wondered. This phase proved most harmful to the Allies. From the moment when Stalin made terms with Hitler the Communists in France took their cue from Moscow and denounced the war as "an imperialist and capitalist crime against democracy". They did what they could to undermine morale in the Army and impede production in the workshops. The morale of France, both of her soldiers and her people, was now in May markedly lower than at the outbreak of war.
Nothing like this happened in Britain, where Soviet-directed Communism, though busy, was weak. Nevertheless we were still a party Government, under a Prime Minister from whom the Opposition was bitterly estranged, and without the ardent and positive help of the trade union movement. The sedate, sincere, but routine character of the Administration did not evoke that intense effort, either in the governing circles or in the munitions factories, which was vital. The stroke of catastrophe and the spur of peril were needed to call forth the dormant might of the British nation. The tocsin was about to sound."
Churchill, Winston S. The Second Wolrd War: The Gathering Storm, 1948. Pages 583-584.