Japan entered the First World War in 1914 on the side of Britain and its allies, mainly to seize German colonies in Asia and the Pacific at low cost. By 1919, Japan came to the Paris Peace Conference as one of the five main victorious powers — a huge change in status from twenty years earlier.
What Japan wanted at Paris: Japan wanted three things: to keep the former German territories it had occupied (Shandong in China, and Pacific islands north of the equator), to be recognised as a great power, and to have a racial equality clause racial equality clause written into the League of Nations Covenant.
Japan got the territories — it kept Shandong and received the Pacific islands as League of Nations mandates. But the racial equality clause was rejected, mainly because Britain's ally Australia and the United States opposed it. This rejection humiliated Japanese leaders and fed a growing sense that the Western powers would never treat Japan as a true equal, however powerful it became.
- Paris Peace Conference (1919) — Japan gained Shandong and Pacific mandates but was refused the racial equality clause
- Twenty-One Demands (1915) — earlier wartime pressure on China that showed Japan's expansionist ambitions and worsened relations with China and the West
- Great power status — by 1919 Japan sat alongside Britain, France, the US and Italy as one of the 'Big Five' at Paris
The Washington Naval Conference (1921–1922)
After the war, the United States, Britain and Japan were building warships at a pace none of them could really afford. The Washington Naval Conference (1921–1922) was called by the US to slow this arms race down and to settle rivalries in East Asia and the Pacific before they turned into another war.
| Agreement | What it meant for Japan |
|---|---|
| Five-Power Treaty | Set a battleship ratio of roughly 5 (US) : 5 (Britain) : 3 (Japan) — Japan accepted fewer capital ships than the US or Britain |
| Four-Power Treaty | Ended the Anglo-Japanese Alliance (in place since 1902), leaving Japan without its main great-power ally |
| Nine-Power Treaty | Confirmed China's territorial integrity and the 'Open Door' — limiting Japan's freedom to expand into China |
Why this mattered later: Many in the Japanese army and navy saw the 5:5:3 ratio and the loss of the British alliance as national humiliations forced on Japan by the West. This resentment became a powerful argument for militarists in the 1930s, who claimed diplomacy had failed to win Japan the respect and resources it deserved.
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The period roughly from 1912 to 1926 is called the Taisho era, named after Emperor Taisho. Historians often call its politics 'Taisho democracy' Taisho democracy — a time when elected politicians and political parties, rather than the military or the old oligarchs, seemed to be gaining real control of government.
- Growth of liberal values — a growing urban middle class, a freer press, and new ideas about democracy and workers' rights spread through Japan's cities
- The two-party system — by the 1920s, two large parties, the Rikken Seiyukai and the Kenseikai (later Minseito), competed to form governments
- Universal male suffrage (1925) — the vote was extended to all men over 25, hugely widening the electorate
- Cabinet responsibility — for the first time, prime ministers were regularly chosen from the majority party in the lower house of the Diet Diet, rather than picked directly by military and court elites
A key figure was Hara Takashi, who became prime minister in 1918 as the leader of the Seiyukai party — the first commoner and first party leader to hold the post. His government expanded education and infrastructure, though he was assassinated in 1921 by a young ultranationalist who believed party politicians were corrupt and weak.
Signs of a more liberal Japan: Alongside party government, the 1920s saw growing trade unions, a more outspoken press, new social movements (including for women's rights, though women still could not vote), and Japanese intellectuals openly debating democracy, socialism and even Marxism.
Democracy had limits: The same year that the vote was widened (1925), the government also passed the Peace Preservation Law, which allowed the arrest of anyone who criticised the emperor system or private property. Taisho democracy expanded political participation while also building tools to crush dissent — a contradiction that made liberal gains fragile.
Forces supporting liberal politics
- Growing urban middle class and press
- Universal male suffrage (1925)
- Party cabinets and Diet politics
- Business and industrial interests wanting stable trade
Forces working against it
- Peace Preservation Law (1925)
- Army and navy kept independent access to the emperor
- Rural poverty untouched by party politics
- Ultranationalist groups hostile to 'corrupt' parties
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From the late 1920s, Taisho democracy came under increasing attack. A mix of economic crisis, army independence, and violent ultranationalism steadily shifted real power away from elected politicians and towards the military.
Why militarism grew
- Economic hardship — the Great Depression (from 1929) hit Japan's silk exports and rural areas hard, making party politicians look useless and radical solutions more attractive
- Independence of the military — under Japan's constitution, the army and navy ministers had to be serving officers and reported directly to the emperor, not to the prime minister, so the military could bring down a cabinet by refusing to supply a minister
- Resentment over Washington and Paris — many officers saw naval limits and the failure of the racial equality clause as proof that only military strength, not diplomacy, would win Japan respect
- Ultranationalist ideology — groups praised the emperor as divine, glorified war and self-sacrifice, and blamed party politicians and big business (zaibatsu zaibatsu) for national weakness
Coups and assassinations
Extreme nationalists increasingly used violence to attack the party system directly, targeting the very politicians and business leaders they blamed for Japan's problems.
| Event | Date | What happened |
|---|---|---|
| Assassination of Hara Takashi | 1921 | Party-government prime minister stabbed by an ultranationalist at Tokyo station |
| London Naval Treaty crisis | 1930 | PM Hamaguchi Osachi accepted further naval limits; shot by a nationalist months later and died in 1931 |
| May 15th Incident | 1932 | Young naval officers assassinated PM Inukai Tsuyoshi, partly over his caution on Manchuria; after this, no party leader served as PM again until after 1945 |
The turning point: After the May 15th Incident (1932), prime ministers were chosen from military figures or 'national unity' compromises rather than party leaders. This effectively ended Taisho democracy — power drifted from the Diet towards the army, navy and militarist officials, setting the stage for the invasion of Manchuria and the wars that followed.
- Increasing army influence in politics — officers acted with growing independence from civilian control, often presenting the government with actions already taken
- Political coups and assassinations — repeated attacks removed moderate leaders and intimidated survivors into silence
- Weak civilian response — governments rarely punished the perpetrators harshly, which only encouraged further violence