Summary
Highlights
World War I began in Europe in 1914 between the Central Powers (Germany, Austria-Hungary, Ottoman Empire) and the Allied Powers (Great Britain, France, Russia, later Italy). President Woodrow Wilson initially declared US neutrality, preferring to stay out of the European conflict to act as a mediator and maintain trade, despite privately sympathizing with the Allies.
Maintaining neutrality became difficult due to three main reasons. First, the US had stronger economic ties with the Allied nations, lending them billions and trading more with them. Second, Germany's policy of unrestricted submarine warfare violated international laws by sinking British ships, including the passenger ship Lusitania in 1915, which killed 128 Americans. This enraged the American public, though Wilson initially secured a temporary agreement from Germany to cease such attacks.
The third and final blow to US neutrality came with the Zimmerman Telegram in February 1917. British intelligence intercepted a message from Germany to Mexico, proposing an alliance. Germany offered Mexico the return of territories lost to the US if the Central Powers won. This, combined with Germany resuming unrestricted submarine warfare and sinking US merchant ships, led Wilson to ask Congress for a declaration of war. Wilson argued the US needed to make the world safe for democracy and shape the post-war order, especially after the Russian Revolution.
Once the US entered the war, Congress passed the Selective Service Act, drafting 3 million men. The American Expeditionary Forces, though not making a significant impact until 1918, decisively tipped the balance towards an Allied victory. Their main contribution was in the Meuse-Argonne Offensive, where over a million US and French soldiers pushed German forces to their breaking point, leading to the end of the war.
Before the war ended, Wilson proposed his Fourteen Points for post-war peace, advocating for self-determination, reduced military spending, and an international ban on secret treaties. Most notably, he proposed a League of Nations for diplomatic conflict resolution. However, Britain and France, having suffered more, were less idealistic. The Treaty of Versailles instead aimed to punish Germany, requiring them to pay reparations, dismember their military and colonial empire, and accept the War Guilt Clause, which contributed to national humiliation and the rise of Nazism.
Despite the European powers signing the treaty, the US Senate refused to ratify it. A major concern was the League of Nations provision. Senators feared that joining such a body would drag the US into future wars without congressional approval, violating constitutional powers. Due to Wilson's failure to include senators in negotiations and his insistence on the League, the US did not join, which significantly weakened the organization's long-term effectiveness.