The League's 1920s Record: Successes and Failures
A Mixed Record
Through the 1920s the League of Nations dealt with dozens of disputes between its members. Some were resolved quickly and quietly — useful evidence of how international arbitration could prevent war. Others exposed a structural problem the League could never escape: when one of the parties to a dispute was a great power, the unanimity rule and the absence of an army left it almost helpless. The five case studies named in the specification — Aaland Islands, Upper Silesia, Vilna, Corfu and Bulgaria — let students see this pattern in miniature.
Three 1920s successes: Aaland Islands (1921), Upper Silesia (1921), Bulgaria (1925). Two failures: Vilna (1920-23) and Corfu (1923). The pattern is unmistakable: the League could resolve disputes between small states; it could not handle great-power aggression.
Aaland Islands, 1921 — Success
The Aaland Islands sit in the Baltic Sea between Sweden and Finland. They were ethnically Swedish but politically part of newly independent Finland. In 1919 almost all the adult islanders signed a petition asking to join Sweden. The dispute was referred to the League. The League’s commission of inquiry recommended that the islands remain part of Finland but be granted local autonomy and demilitarised. Both states accepted the ruling. The Aalands have remained autonomous Finnish territory ever since — a textbook case of arbitration working between two small, well-behaved states.
Upper Silesia, 1921 — Success
Upper Silesia was an industrial region claimed by both Germany and the new Polish state. It was ethnically mixed and economically valuable, with major coal and steel industries. The League organised a plebiscite in March 1921. Voters split — roughly 60% chose Germany, 40% Poland — and the League decided to partition the region. Germany took the larger area but Poland received the most industrially valuable part. Neither country was happy, but both accepted. The dispute was contained.
In October 1925 a frontier incident in which a Greek soldier was shot dead led to a Greek invasion of southern Bulgaria. Bulgaria appealed to the League. The Council acted swiftly: it ordered Greece to withdraw, agreed compensation of around £45,000 to be paid by Greece to Bulgaria, and threatened sanctions if Greece refused. Greece complied. The episode showed the League at its best when both states were small — and Greek diplomats privately resented being treated more harshly than Italy had been over Corfu only two years earlier.
Vilna, 1920-23 — Failure
Vilna (today’s Vilnius) was the historic capital of Lithuania but had a Polish-speaking majority. After the First World War, both Poland and the new Lithuanian state claimed it. In October 1920, Polish General Lucjan Żeligowski seized Vilna in a stage-managed ‘mutiny’, with the quiet approval of the Polish government. Lithuania appealed to the League, which condemned the seizure and called on Poland to withdraw. Poland refused.
The League had no troops to send and no appetite for sanctions against Poland, which was a key French ally against Bolshevik Russia. After three years of fruitless mediation, the League simply gave up and accepted the Polish occupation in 1923. Vilna remained Polish until the Second World War. The lesson was clear: when a member behaved badly and a great power tacitly backed it, the League had no answer.
In August 1923, an Italian general working on a Greek-Albanian border commission was murdered. Mussolini blamed Greece — without evidence — and demanded an apology and 50 million lire in compensation. When Greece refused, Mussolini ordered the bombardment and occupation of the Greek island of Corfu, killing several civilians. Greece appealed to the League. The Council was preparing to side with Greece when the dispute was suddenly transferred to the Conference of Ambassadors, an Allied body outside the League. The Conference essentially gave Mussolini what he wanted: Greece had to apologise and pay 50 million lire. Italy then withdrew from Corfu. Mussolini drew a clear lesson — the League could be sidestepped.
Humanitarian Successes Beyond the Headlines
Beyond the named case studies, the League’s specialist agencies kept working through the decade. The High Commission for Refugees, led by Norwegian explorer Fridtjof Nansen from 1921, issued Nansen passports to hundreds of thousands of stateless people displaced by war and the Russian Civil War, and helped repatriate roughly 425,000 prisoners of war. The Health Committee fought typhus and cholera epidemics in eastern Europe and helped contain plague outbreaks in Greece. The Slavery Commission contributed to the formal end of slavery in Sierra Leone and brought international pressure on Liberia and Ethiopia. The International Labour Organization (ILO) secured 17 conventions on hours of work and the protection of women and children in industry. These successes were durable: many of these agencies would outlive the political League and form the foundation of the United Nations system created in 1945. But humanitarian work could not save the League’s political reputation in the 1930s when a great power finally tested the collective-security system.
The 1920s record exposed a structural exemption: when a great power was the aggressor (Italy at Corfu) or backed the aggressor (France behind Poland at Vilna), the League could not enforce its own decisions. This pattern would resurface fatally in Manchuria and Abyssinia.