Interwar Diplomacy and Disarmament

Why negotiation mattered after the First World War

The peace settlement had ended the fighting, but it had not removed disagreements between countries. Germany resented the Treaty of Versailles, while France remained concerned about its security. Reparations—the payments Germany owed for war damage—were a particularly serious source of tension.

Internationalist diplomacy offered a different way forward: countries could negotiate compromises instead of relying on threats or force. During the 1920s, agreements addressed three connected problems: Germany’s ability to pay reparations, relations between Germany and its neighbours, and the danger of another arms race.

These agreements were not all organised by the League of Nations. The USA, an important source of money and a major naval power, was not a League member. Direct negotiations allowed countries to involve it and to tackle particular problems outside the League’s machinery. Co-operation outside the League could therefore help international relations without demonstrating that the League itself was effective.

The Dawes Plan, 1924: easing the reparations crisis

In 1923, French occupation of the Ruhr, Germany’s important industrial region, and German hyperinflation had intensified the reparations dispute. Hyperinflation meant that prices rose extremely rapidly and money lost its value. Demanding payments from an economically unstable Germany did little to create a workable settlement.

The Dawes Plan of 1924, developed under the American banker Charles G. Dawes, made Germany’s annual reparations payments more manageable, initially lowering them. It also arranged American bank loans to support German industry.

The connection between these measures mattered. Loans helped Germany rebuild production and earn income, making reparations easier to pay. More manageable payments, in turn, reduced confrontation with the Allies. The settlement helped resolve the Ruhr crisis, with France agreeing to withdraw, and improved trust between Germany and the Allies.

However, this was not the cancellation of reparations. Nor was recovery entirely secure: Germany became dependent on American lending. If those loans stopped or were recalled, the economic foundation of improved relations would be threatened. The plan brought practical relief, but also created a vulnerability.

Locarno, 1925: Germany returns to negotiated diplomacy

Economic recovery made political reconciliation easier. At Locarno in October 1925, Germany, France, Belgium, Britain and Italy negotiated agreements intended to reduce tension in Western Europe. Gustav Stresemann, Germany’s foreign minister, sought to improve Germany’s international position; French foreign minister Aristide Briand sought better relations and greater security.

Germany accepted its western borders with France and Belgium established by the Versailles settlement. Germany, France and Belgium promised not to attack one another and to settle disputes peacefully. The agreements also reaffirmed the demilitarisation of the Rhineland: Germany was not permitted to station military forces or build fortifications there.

Britain and Italy acted as guarantors of this western settlement. They undertook to help the victim of an attack that violated the treaty, whether that victim was Germany, France or Belgium. This gave France reassurance against German aggression, while also offering Germany protection against an attack by its western neighbours. The treaty provided for League consideration of breaches and assistance following its findings, with immediate help in cases of clear aggression requiring urgent action. Although negotiated separately, Locarno therefore worked within the League’s framework rather than simply bypassing it.

Locarno differed importantly from Versailles. Germany participated in negotiation as an equal rather than simply receiving terms imposed by the victors. This helped make international co-operation more acceptable and restored Germany’s reputation. Germany joined the League of Nations in September 1926, strengthening the sense that it was returning to the international community. The resulting optimism became known as the ‘spirit of Locarno’.

However, Germany’s eastern borders with Poland and Czechoslovakia did not receive an equivalent guarantee. Stresemann kept open the possibility of changing them, so the improved security of Western Europe did not extend equally to Eastern Europe. This was a major limitation: Locarno reduced one source of tension without settling all disputes over Germany’s borders.

Reconciliation also did not mean that all Germans accepted the peace settlement. Extremist parties opposed acceptance of the Versailles borders. Locarno represented a significant improvement in relations, not the disappearance of disagreement over Germany’s post-war position.

The Kellogg–Briand Pact, 1928: renouncing war

Briand and the American Secretary of State, Frank B. Kellogg, helped develop a wider declaration against war. In the Kellogg–Briand Pact, first signed by fifteen countries in Paris on 27 August 1928, participating countries renounced war as an instrument of national policy and promised to settle disputes peacefully. Germany was among the original signatories, and many more countries subsequently joined.

Its importance lay in the breadth of the ambition. Instead of addressing only reparations or particular borders, it sought to establish peaceful settlement as a principle of international relations. American involvement also showed that the USA could support international co-operation despite remaining outside the League.

For Germany, participation reinforced its recognition as a respectable state able to negotiate alongside other powers. But the pact must not be confused with a disarmament agreement. It did not require countries to reduce their weapons, and it did not remove Germany’s military restrictions under Versailles. A promise to avoid war and a practical reduction in the ability to fight were different things.

The pact also had serious enforcement weaknesses. There was no agreed mechanism for imposing punishments on countries that broke it, and signing did not oblige the USA to take action against an aggressor. Its success therefore depended heavily on governments choosing to honour their promises.

Furthermore, countries retained the right to fight in self-defence, but the meaning of self-defence was not clearly defined. A government could claim that its military action was defensive rather than admit that it was aggression. This made the promise easier to evade. Japan’s invasion of Manchuria in 1931, despite having signed the pact, demonstrated that condemnation of war was not enough to prevent it.

The Young Plan, 1929: a longer-term reparations settlement

The Dawes Plan had eased the immediate payments problem. The Young Plan of 1929, developed under American banker Owen Young, went further by reducing Germany’s total reparations bill and extending repayment to 1988.

This lightened the financial burden and improved relations between Germany and the Allies. The settlement was also associated with the early withdrawal of French troops from the Rhineland in 1930. Ending foreign occupation and keeping the Rhineland demilitarised were separate matters: withdrawal did not mean Germany was free to station troops there.

German extremist parties nevertheless opposed the plan because it kept reparations in place for decades. Hitler criticised it as passing the burden to future generations. Thus, an agreement could be a diplomatic achievement while remaining politically controversial within Germany.

Naval disarmament: a limited achievement in 1922

Disarmament aimed to reduce military competition and the danger of war. It required more than peaceful language: governments had to accept restrictions on their own forces.

The Washington Conference of 1921–1922 brought together major naval powers, including the USA, Britain, Japan, France and Italy. The resulting naval agreement restricted the construction and tonnage of major warships, including battleships and aircraft carriers. It sought to ease naval rivalry and tension in the Pacific.

This was a concrete achievement because it placed limits on military equipment. However, it was not complete naval disarmament. Restrictions on major warships left room for competition in lighter vessels. Nor did an agreement about navies settle the problem of land armies. Washington showed that negotiated arms limitation was possible, but only within an agreed scope.

The World Disarmament Conference, 1932–1934

The League’s World Disarmament Conference opened in Geneva in 1932 and continued until 1934. Its central difficulty was the relationship between disarmament and security: governments were reluctant to reduce their forces unless they believed other countries would not threaten them.

Germany had already faced military restrictions under Versailles. German representatives argued that other countries should disarm to Germany’s level. France resisted because it feared that reducing its own forces would leave it vulnerable to Germany. What Germany presented as equal treatment could therefore look to France like a loss of protection.

After coming to power in 1933, Hitler claimed that Germany would refrain from rearmament if other countries destroyed their weapons within five years. Germany was already secretly rearming, so his stated offer must be distinguished from his actual policy. France, Poland and Czechoslovakia feared for their security and refused the proposal. Hitler used the dispute to justify Germany’s withdrawal from the conference and the League in 1933.

Japan’s aggression in Manchuria also weakened confidence in collective security. If the League could not restrain a powerful aggressor, countries had less reason to believe that disarming would make them safer. The conference ended in failure in 1934.

How far had diplomacy succeeded?

The agreements of the 1920s produced real improvements: reparations became more manageable, Germany returned to international negotiation, and naval competition was restricted. These were practical changes, not merely expressions of hope.

Yet their achievements differed. The Dawes and Young Plans addressed financial problems; Locarno offered guarantees for Western Europe but not equivalent protection for Germany’s eastern borders; Kellogg–Briand expressed opposition to war without an effective enforcement mechanism; Washington imposed limited naval restrictions. None should be treated as a complete solution to international conflict.

The failure of wider disarmament exposed the underlying problem. Countries wanted peace, but disagreed about what would keep them secure. Where trust was weak, governments were unwilling to give up military strength. Co-operation had improved international relations without removing their economic and political fragility.

Four agreements to recall

• Dawes Plan, 1924: more manageable annual reparations and American loans to German industry. Eased tension and supported recovery, but increased dependence on US lending.
• Locarno, 1925: Germany accepted its western borders with France and Belgium; Britain and Italy guaranteed the settlement. Rhineland demilitarisation reaffirmed; Germany joined the League in 1926. Eastern borders with Poland and Czechoslovakia lacked an equivalent guarantee.
• Kellogg–Briand Pact, 1928: renounced war as national policy and promised peaceful dispute settlement. No agreed punishment mechanism, an unclear self-defence exception and no requirement to disarm limited its effectiveness.
• Young Plan, 1929: reduced the total reparations bill and extended repayment to 1988. Improved relations, but German extremists opposed continuing reparations.

Disarmament: achievement and failure

• Washington, 1921–1922: limits on major warships. Practical but partial; competition in lighter vessels remained possible.
• Geneva, 1932–1934: World Disarmament Conference failed. Germany demanded equal treatment; France feared losing security. Hitler used the dispute to justify withdrawal in 1933, while secretly rearming.
• Manchuria: the League’s inability to restrain aggression weakened confidence that disarmament would be safe.

Overall judgement

Diplomacy achieved financial relief, reconciliation and limited arms control. Economic dependence, unequal security guarantees, weak enforcement and mistrust prevented lasting security.