The Age of Imperialism ended with the appearance of warfare the likes of which the world had never seen: new machines for killing the enemy through gas and other means, wholesale destruction of villages and the countryside in battle zones, as well as mass civilian deaths and the uprooting of people's lives.
The major empires which had existed prior to the war – Ottoman, German, and Austro-Hungarian – were no more. Many of their territories, including colonies, were divvied up among the major powers despite the hopes of the people in those regions for freedom. Colonies which had participated in the war in hope that they would receive increased autonomy began to push for independence when it did not happen.
Cartoon from Punch Magazine 1919 spoofing the U.S. for not joining the Leage of Nations
The outcome of the peace conference when the Big Four met at Versailles was the Treaty of Versailles. This document had a number of controversial terms for peace. Germany had to accept responsibility for the war, lose territory, pay reparations of 30 billion dollars, and reduce the size of its military.
Out of President Wilson’s Fourteen Points, only one was included in the treaty - the League of Nations. Comprised of over 40 nations, this organization was established as an international body to resolve conflicts and prevent future wars. The League was limited in its effectiveness because the U.S. did not join and it did not have the power to enforce its decisions.
The treaty also established the mandate system to avoid future conflicts. Great Britain and France divided up large portions of the Ottoman Empire in the Middle East and Germany's African colonies between themselves. Great Britain maintained control over Iraq, Transjordan, and Palestine, while France controlled Syria and Lebanon. Great Britain and France were to monitor these countries until they became independent, however, these powers had little interest in giving up these territories. The division of the Ottoman Empire through the mandate system planted the seeds for future conflict in the Middle East. The war transformed European and American life, wrecked the economies of Europe, and planted the seeds for a second world war.