When Emperor Hirohito ascended to the throne in 1926, Japan was enveloped in a struggle between liberals and leftists on one side, and ultraconservatives on the other. In 1925, universal male suffrage was introduced, increasing the electorate from 3.3 to 12.5 million. Yet as the left pushed for further democratic reforms, right-wing politicians pushed for legislation to ban organisations that threatened the state by advocating wealth distribution or political change. This resulted in 1925's 'Peace Preservation Law', which massively curtailed political freedom.
As the left disintegrated, ultra-nationalism began to loom large. Japanese nationalism was born at the end of the nineteenth century. During the Meiji period, industrialisation, centralisation, mass education and military conscription produced a shift in popular allegiances. Feudal loyalties were replaced by loyalty to the state, personified by the Emperor.
Although early ultra-nationalists called for a tempering of Japan's 'westernisation', through limits on industrialisation, their focus changed after the First World War. Western politicians criticised Japan's imperial ambitions and limited Japanese military expansion (in 1922's Five Power Naval Limitation Agreement). The 1924 Japanese Exclusion Act prohibited Japanese immigration into the US. Ultra-nationalists saw these actions as provocative; they moved towards xenophobic, emperor-centred and Asia-centric positions, portraying the 'ABCD Powers' (America-British-Chinese-Dutch) as threatening the Japanese Empire.
Between 1928 and 1932, Japan faced domestic crisis. Economic collapse associated with the Great Depression provoked spiralling prices, unemployment, falling exports and social unrest. In November 1930, the Prime Minister Hamaguchi Osachi was shot by an ultra-nationalist. In summer 1931, as control slipped away from the civilian government, the army acted independently to invade Manchuria. Troops quickly conquered the entire border region, establishing the puppet state of Manchukuo. Though the League of Nations condemned the action, it was powerless to intervene, and Japan promptly withdrew its membership. International isolation fed ultra-nationalism. Mayors, teachers and Shinto priests were recruited by ultra-nationalist movements to indoctrinate citizens.
In May 1932, an attempt by army officers to assassinate Hamaguchi's successor stopped short of becoming a full-blown coup, but ended rule by political parties. Between 1932 and 1936, admirals ruled Japan. Within government, the idea of the 'Greater East Asian Co-Prosperity Sphere' emerged. This plan called for Asian unification against western imperialism under Japanese leadership, leading to Asian self-sufficiency and prosperity. In reality, it meant an agenda of Japanese imperial domination in the Far East.
In July 1937, Japanese soldiers at the Marco Polo Bridge on the Manchuria border used explosions heard on the Chinese side as a pretext to invade China. The offensive developed into a full scale war, blessed by Hirohito. Japan enjoyed military superiority over China. The army advanced quickly and occupied Peking. By December, the Japanese had defeated Chinese forces at Shanghai and seized Nanking. There Japanese troops committed the greatest atrocity of an incredibly brutal war: the 'Rape of Nanking', in which an estimated 300,000 civilians were slaughtered.
By 1939, the war was in stalemate; Chinese Communist and Nationalist forces continued to resist. Yet Japanese imperial ambitions were undimmed. In 1940, Japan signed the Tripartite Pact, creating the Rome-Tokyo-Berlin Axis, building on the alliance created in 1936 by the Anti-Comintern Pact. Japan now looked hungrily towards the oil-rich Dutch East Indies to fuel its Co-Prosperity Sphere. In 1941, when Imperial General Headquarters rejected Roosevelt's ultimatum regarding the removal of troops from China and French Indochina, the US President announced an oil embargo on Japan. For Japan, the move was the perfect pretext for war, unleashed in December 1941 with the Pearl Harbor attack.