Opponents of the war in August 1914 were in a small minority. As Ramsay MacDonald asserted gloomily at this time, the conflict with Germany 'would be the most popular war [Britain] had ever fought'. Shortly after Britain's entry into the war, he resigned the Labour Party leadership to the pro-war Arthur Henderson.

Anti-war voices in both the Labour and Liberal parties, which had been numerous during the July crisis, largely disappeared after 4 August. In the press and among the general public, too, a pro-war consensus quickly became apparent. The anti-war appeal to British workers in the 6 August issue of the Labour Leader, the newspaper of the Independent Labour Party (ILP), fell on deaf ears.

In 1915, however, the patriotic unity of August 1914 began to dissipate. Anti-war voices, though diverse and relatively few in number, gained greater authority. Dissenters ranged from pacifists opposed to all war on principle to those who merely disagreed with the government about how the present war should be conducted and concluded.

By October, the Labour Leader had doubled its pre-war circulation figures to more than 40,000. Aside from the ILP, issues relating to the damaging conduct of the war through 'secret diplomacy' and the need to avoid a vindictive peace were raised by a more select group of prominent intellectuals and politicians. Formed in August 1914, the Union of Democratic Control (UDC). numbered among its members MacDonald, Norman Angell and Bertrand Russell.