Chapter 4 examines the influence of the Bryce Group’s war prevention plan more broadly, scrutinising the relationship between the League of Nations Society and its counterpart in the United States, the League to Enforce Peace. While scholars have hardly analysed the two groups’ interactions, both groups sprang from the liberal internationalist tradition, had a lot in common in terms of social background and worked for the same aim of reforming the global order. Such similarities, however, did not enable them to establish a constructive collaboration, let alone a transnational movement. In reality, both groups sought political support for their own post-war schemes and regarded their counterpart merely as a medium for approaching statesmen on the other side of the Atlantic. Moreover, the differences in their domestic contexts and in the British and American liberal internationalist traditions hindered the two groups from building mutual trust and a joint lobbying strategy.

Building on the Bryce Group’s post-war plan, the League of Nations Society was founded in 1915 to promote a peaceful organisation to the public. After the Society’s first public meeting in May 1917, the pro-league movement successfully evolved from a small circle to a mass movement that mobilised the public to establish a league. Previous studies have, therefore, regarded May 1917 as a positive turning point of the movement and mainly focused on widespread support for the league thereafter. Yet, the year 1917 also marked the time when the originators of the movement began to lose control of defining what the league would be like. To communicate to the general public, the Society simplified its ideas by underscoring only the creation of an international organisation without going into details. It led the movement to abandon its original, sophisticated discussions about a new order, which became accelerated in the following years.

Chapter 5 demonstrates how the league of nations became an important political issue in 1917–1918. While the pro-league movement succeeded in attracting public attention for the post-war plan, pro-leaguers came to promote a conception of the league that they had opposed in 1914–1915: a league of victorious powers aligned against Germany. Begun as a reaction against anti-German jingoism and the balance-of-power politics, the movement initially aspired to change the norms of international relations by creating a new institution comprised of all the great powers. Yet by 1918, the activists had come to promote the league as a continuation of the war-time alliance, backed by a powerful argument both to defeat Germany and to form the league as a coalition of democratic states. An extension of the war-time politics, not the yearning for peace as scholars have supposed, led to the creation of the League of Nations.