Woodrow Wilson's supreme goal in World War I was to broker an effective and lasting peace. He enumerated his war aims in his famous Fourteen Points speech, with the last point calling for the creation of a League of Nations. At the Paris Peace Conference in 1919, he fought hard, but was not able to incorporate his Fourteen Points in the treaty. He did, however, make sure the League of Nations was an inextricable part of the final agreement. He hoped that once the League was established, it could rectify the treaty's many shortcomings

Of the treaty's 440 articles, the first twenty-six comprise the Covenant of the League of Nations. This covenant describes the operational workings of the League. Article Ten obliges signatories to guarantee the political independence and territorial integrity of all member nations against outside aggression, and to consult together to oppose aggression when it occurs. This became the critical point, and the one that ultimately prevented the treaty's ratification by the Senate.

Senator Henry Cabot Lodge led the opposition. Lodge and Wilson were bitter political foes, but they also had legitimate differences of views on the League and on the covenant's Tenth Article. Lodge believed that the League, under Article Ten, could require the United States to commit economic or military force to maintain the collective security of member nations. Wilson did not share this interpretation of Article 10 - an article that Wilson had written himself. Wilson stated that the veto power enjoyed by the United States in the League Council could prevent any League sanction, but if a unanimous League voted sanctions, the vote amounted only to advice, in any case. The United States would not be, therefore, legally bound to the League's dictates. However, Wilson did declare, that the United States would be morally bound to adhere to the League's resolutions. A moral bond was, for Wilson, infinitely superior to a mere legal one. Article Ten was, for him, "a very grave and solemn obligation."

Wilson and Lodge surely could have found a middle ground. Some sort of compromise language could have been drafted. There were pro-treaty Republicans who could have formed a coalition with the Democrats to win the necessary two-thirds majority. But Wilson blocked compromise after he suffered a massive stroke in October 1919. No accommodation with the opposition was found on either side. The treaty was voted down.

The United States remained officially at war until June of 1921 when President Warren Harding approved a joint congressional resolution proclaiming the war with the Central Powers ended, and later signed a separate peace treaty. The resolution and the treaty specified that although the United States was not a party to the Versailles Treaty, it retained all rights and advantages accorded to it under the pact's terms, excluding the League Covenant. The United States never joined the League of Nations