There were several major developments between 1902 and 1939. These included the search for collective security throughout the 1920’s, the signing of the Versailles treaty in 1919, the series of ententes signed between 1902 and 1907, as well as the rise of Germany, which culminated in both world wars, between 1905 and 1939.
The search for collective security, which was seen during the 1920’s, was symbolised by Britain joining the League of Nations. The league was the idea of Woodrow Wilson, following the First World War. Wilson believed in peace, and collective security. The idea behind the league was that countries could discuss disputes, and as punishment economic sanctions could be placed upon a country, leaving war to be a last resort. However, after America refused to join the league, due to not wishing to have the possibility of being dragged into another war (with the horrors of the First World War still fresh in minds and hearts) the league lost most of its ability to deal with issues. Britain never fully gave support to the league, although vocally she did, in reality Britain far preferred working independently of Europe. This left the league powerless against the rise of Hitler’s Germany during the 1930’s, as well as with fascist Japan and Italy, leaving the Second World War inevitable.
Other than the search for collective security, the 1920’s and 1930’s saw Britain desperately attempting to preserve her empire, her economy, and the balance of power in Europe. One example of this was Britain refusing to allow France to build a channel tunnel, or sign an alliance with France, as at one point France was seen as a bigger threat to the balance of power than that of Germany herself. This was also due to Britain not seeing herself as a member of the League of Nations, but rather as her own world power. Britain also supported many of the efforts to help Germany’s economy during the 1920’s, such as the Dawes plan and the young plan. France did not agree with this at all, as it strengthened the German economy significantly, allowing her to rebuild her country. In many respects Britain were far too worried about France, while giving Germany too much opportunity to rebuild herself.
However, following this, throughout the 1920’s and 1930’s Germany began to rise to power again. The Versailles treaty had created a massive desire for revenge among the German people, and Hitler conveyed this message of despise to the world. He quickly began revising the treaty, by rearming his military and navy in 1935, by creating an anschluss with Austria in 1938 and by remilitarizing the Rhineland in 1936. The League of Nations was helpless against this, as it possessed virtually no power without backing from America or Britain. Britain followed a policy of appeasement towards the Germans, mostly out of fear of a second world war, however, following the attack on Poland in 1939 Britain was forced to go to war with Germany, as she had deeply upset the balance of power, and posed a threat to the British Empire.
Despite the fact that these were indeed major developments during the period of 1902 – 1939, there was also a major development during the first decade of the century, with a series of ententes being signed with Japan in 1902, France in 1904 and Russia in 1907. All of these agreements were aimed at strengthening the British Empire, and protecting the balance of power. Undoubtedly, the most important of these ententes was the entente with France in 1904, which by 1912 had become an informal alliance. This followed the entente surviving the German attempts of destroying it, through the Moroccan crises of 1905 and 1911, whereby Germany attempted to gain control of morocco, despite France and Britain having agreed that France should get control of all trading links in morocco.
Despite all of these, the major development during the period of 1902 – 1939 has to be the rise of Germany, and the German question. Both the rise leading to world war one, led by Kaiser Wilhelm, and the rise leading to world war two lead by Hitler are of fairly equal importance, although it could be argued that the first of these rises led to the second, meaning it is of slightly higher importance. This also added a newfound relevance to the series of ententes signed between 1902 and 1907, as they allied a majority of Europe against Germany. Collective security was a big development, however at the time it was a fairly catastrophic failure. The Versailles treaty was also important, although Britain did not become too involved in enforcing these terms until it was too late to stop a full scale war.