Key Question 2 · 1920–1929
Successes & Failures in the 1920s
The League resolved genuine disputes in the 1920s — but its failures revealed the limits of collective security from the very start. Cambridge expects you to explain WHY it worked when it did, not just that it did.
Section 1
Successes
The League resolved several disputes in the 1920s. In each case, learn what happened, who was involved, and — crucially — why the League's decision was accepted.
Aaland Islands (1921)
Both Finland and Sweden claimed the Aaland Islands, a strategically placed archipelago in the Baltic. The League awarded the islands to Finland, with guaranteed cultural protections for the Swedish-speaking population. Sweden accepted the ruling. Neither state resorted to force — the League arbitrated before aggression occurred.
- ✦ Both parties were minor powers — neither could defy the League
- ✦ No great power had a strategic interest in the outcome
- ✦ Cultural protections made the ruling acceptable to Sweden
Upper Silesia (1921)
Upper Silesia was an industrially rich region claimed by both Germany and Poland after WWI. A plebiscite was held under League supervision. When the vote produced an unclear result, the League partitioned the territory between the two states along ethnic and industrial lines. Both Germany and Poland accepted the ruling.
- ✦ League stepped in when the plebiscite result was disputed — prevented escalation
- ✦ Germany was weakened post-war and not yet in a position to defy international rulings
- ✦ Both sides accepted an imperfect compromise
Greco-Bulgarian Border (1925)
Greece invaded Bulgaria following a border incident. The League condemned the invasion, ordered Greek forces to withdraw, and demanded Greece pay compensation to Bulgaria. Greece complied. This was the clearest example of the League enforcing collective security successfully — an aggressor was identified, condemned, and made to back down.
- ✦ Both Greece and Bulgaria were minor powers — neither had great-power protection
- ✦ Greece faced unified condemnation with no ally to shield it
- ✦ The cost of compliance (withdrawal + compensation) was low compared to defiance
Section 2
Failures
Even in the 1920s the League could not compel determined aggressors — especially when a major power was involved. These failures set a precedent that was not lost on Hitler and Japan.
Vilna (1920)
Poland seized Vilna — the historic capital of Lithuania — by force in 1920. The League condemned the action and demanded Poland withdraw. Poland refused. The League did nothing further. Vilna remained under Polish control. No sanctions were applied, no military force was threatened, and the episode passed without consequence for Poland.
- ✦ Exposed the limits of moral condemnation when an aggressor simply ignored it
- ✦ Britain and France had no appetite to confront Poland — a potential buffer against the USSR
- ✦ The pattern: condemnation without enforcement = no deterrent
Corfu Incident (1923)
When Italian officials were killed on Greek soil while marking the Greek-Albanian border, Mussolini demanded reparations and, when Greece refused, bombarded and occupied the Greek island of Corfu. The League condemned Italy. But Britain and France — reluctant to alienate a potential ally against Germany — pressured Greece to pay compensation to Italy and apologise. Italian forces then withdrew, having effectively won.
- ✦ A permanent Council member (Italy) defied the League — and faced no real penalty
- ✦ The victim (Greece) paid compensation to the aggressor (Italy)
- ✦ Britain and France prioritised great-power politics over the League's principles
- ✦ The lesson was not lost on Hitler and Japan: major powers could bully small states and face no serious consequence
Section 3
Why Did It Work in the 1920s?
What made 1920s disputes different?
The League's successes in the 1920s all had one thing in common: they involved minor powers with no great-power backing on either side. Minor powers were more likely to accept League rulings because they lacked the military strength to defy them and had no powerful ally willing to protect them if they refused.
In Aaland, Finland and Sweden were small states with no patron. In Upper Silesia, Germany was weakened and isolated. In the Greco-Bulgarian dispute, Greece faced unified condemnation with no shield. In each case, compliance cost the losing state less than defiance would have.
Corfu showed exactly what happened when a major power was determined to get its way. Italy was a permanent Council member. Britain and France needed it as a potential counterweight to Germany. Collective security was sacrificed for great-power diplomacy — and the outcome rewarded the aggressor. This pattern would repeat, far more destructively, in the 1930s.
Section 4
Examiner Warnings
The 1920s and 1930s are examined separately. Mixing them up is one of the most common timeframe errors in KQ2.
Examiner Warnings — KQ2: The League in the 1920s
Cambridge 0470 ER 2021–2025-
Questions about the League in the 1920s must NOT include Manchuria or Abyssinia. Manchuria was 1931–33; Abyssinia was 1935–36. Both are 1930s events. Using them in answer to a question specifically about the 1920s is irrelevant and will be penalised. Always check the date range of the question before selecting your evidence.
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Corfu (1923) is a 1920s failure — but check the question's date range before including it. If the question asks about the League in the 1920s, Corfu is relevant and important. If the question asks about a specific year range that excludes 1923, leave it out.
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Vilna (1920) is frequently confused with the Aaland Islands dispute. These are entirely different events in different countries. Vilna = Poland seizing Lithuania's capital city; Aaland = a Finnish–Swedish dispute over Baltic islands resolved peacefully. Do not mix them up.
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The League handled approximately 66 international disputes between the wars and succeeded in roughly half. This statistic is useful for (b) and (c) answers to show the League had a genuine but partial record of success — it is more sophisticated than simply saying 'the League succeeded in the 1920s and failed in the 1930s'.
Section 5
Exam Focus
Cambridge tests 1920s disputes across all three question types. Know the specific details of each case — vague references to 'disputes it settled' score Level 2 at most.
What / Describe questions
- ✦ What was the Aaland Islands dispute?
- ✦ What happened at Corfu?
- ✦ Describe one success of the League in the 1920s.
Name the dispute, state who was involved, what happened, and what the outcome was. Two specific points. No analysis required — but vague answers score 1–2 only.
Why / Explain questions
- ✦ Why did the League have some success in the 1920s?
- ✦ Why was the Corfu incident important?
Two developed reasons, each with specific evidence. WHY, not WHAT. For Corfu: significance = it showed major powers could defy the League and face no real penalty.
How far / Judgement questions
- ✦ How far was the League of Nations a success?
- ✦ Was the League's structure or the behaviour of members more to blame for its failures?
Use 1920s successes as evidence for one side and 1930s failures for the other. A Level 5 answer explains WHY the same structure produced different results in each decade.
The Key Analytical Move Cambridge Rewards
Level 2: "The League had some success because countries accepted its decisions."
Level 3+: "The League succeeded because disputes involved minor powers who lacked the military strength to defy it, and no major power had a strategic interest in the outcome. When a major power (Italy at Corfu) was involved and Britain and France valued that power's friendship, collective security was abandoned."
The distinction matters for (c) answers: the structure did not change between 1921 and 1935. What changed was the scale of the aggressor, the stakes for the major powers, and the impact of the Depression on member states' willingness to act. That explanation — not just a list of successes and failures — is what reaches Level 4 and Level 5.