The First World War (1914-18), a.k.a. The Great War, was an epochal moment in world history. It brought the long 19th century to an end and marked the beginning of the 20th. It wrote finis to the Gilded Age and its sanguine optimism. Its political and economic effects were felt throughout the remainder of the century and they continue even today. In this respect, we are still living in an even longer 20th century. War or the threat of war have persisted from then until now, as have most of the social and economic ills that followed in its train. It caused the Great Depression, Totalitarianism, the Second World War and its aftermath. 
And yet it was a most unlikely war. In 1910, British journalist Norman Angell published a book entitled “The Great Illusion.” The theme of the book was the unlikelihood of war among European nations. In the aftermath of the war, Angell and his book were dismissed with scorn by many. But more sympathetic readers have countered that this is because his critics missed Angell’s irony and the subtlety of his argument. 
His theme was not a thesis; he did not argue that war was unlikely, but that, for their best interests, national leaders must consider it unlikely. He argued that because of the commercial and economic interdependence of the nations of Europe, Europe had become a community with shared interests; there was no need for separate nations to possess standing armies to defend themselves against their neighbors, nor was there need for them to seek an increase of territory at their neighbors’ expense, for their destinies had become intertwined.
Europe had become a vibrant economic community; therefore, for European nations to make war against each other would be suicidal. He concluded that it would be irrational for any European nation to make aggressive war against its neighbors, and that wars of self defense were therefore unnecessary, as were the building up of great standing armies. It was a sound argument then, and it remains so today, one well worth retrieving and directing against proponents of the new nationalism and militarism. It follows that the so-called Great War was a tragic absurdity. The most difficult task for historians of the First World War has been to explain why it happened. 
The war was the chief cause of the change in the character of Woodrow Wilson’s presidency from triumph to tragedy.
Wilson’s first response to the war was to keep America out of it, and to maintain a strict neutrality towards the belligerents. These were the Central Powers, consisting of Austria-Hungary, Germany, Bulgaria and the Ottoman Empire, and the Triple Alliance, or the Entente or Allies for short, comprising France, Russia and the United Kingdom. His chief aim was peace, and it remained his abiding hope. He offered himself to the warring parties as an impartial mediator. His concern went well beyond persuading them to meet together and settle their differences. His goal was a durable peace among all nations, the end of war and the threat of war, and to achieve this, it was necessary to create a supra-national institution to enforce peace, a league of nations endowed with superior force. 
“It will be absolutely necessary that a force be created as a guarantor of the permanency of the settlement so much greater than the any nation … or any alliance [of nations]…. If the peace to be made is to endure, it must be a peace made secure by the organized major force of mankind.”
The force he intended was not military, but the rule of law, much as our Constitution is sovereign over states. It required an international covenant of peoples.
Wilson was following in the footsteps of Thomas Hobbes. He imagined the current international condition to be “a state of nature,” a state of war of all against all, which could be ended by acknowledging a superior power guided by law, a law of nature that prescribed “Make peace and keep it.”
He met with no success. And Germany challenged his impartiality beyond all rational limits. The German U-boat campaign against trans-Atlantic shipping caused the loss of American lives. Then there was the notorious Zimmerman affair, in which Germany, foreseeing American entry into the war, tried to induce Mexico to declare war against the United States, promising as a reward the return of territories lost in the Mexican War: Texas, Arizona and New Mexico. On April 2, 1917, Wilson asked Congress to declare war, and the United States joined the Allies. “And the war came.”
Yet Wilson did not forget his plan; he expanded and refined it. When the war ended, he led the American delegation to the Paris Peace Conference, convened in January 1919. Among the goals he sought were the restoration of territories lost during the war; guarantees of autonomy to all nations; free trade; and a League of Nations, open to all nations. He resisted, in vain, the demands of France and Britain to punish Germany, and although agreement was reached to create a League of Nations, its powers were not as great as he desired. 
When he returned to the United States, he was met with strong opposition to the League. His chief opponent was Sen. Henry Cabot Lodge; another was Theodore Roosevelt. The issue was sovereignty, and it pitted nationalists against internationalists. Nationalists contended that membership in the League would limit the sovereignty of nations. Internationalists did not deny this, but contended that it was necessary to create a lasting peace. It was the only means to end chronic war. 
Wilson went on a nationwide campaign for American entry into the League. His effort failed as did his health. He suffered a stroke, and returned to Washington; thereafter he was dependent on others to perform the duties of his office until his term ended in March 1921.
Postscript: “The Great Illusion” is available online @gutenberg.org. In 1931, Norman Angell was knighted, and in 1933 he was awarded the Nobel Peace Prize. Key writings by Wilson are provided in “Woodrow Wilson: Essential Writings and Speeches of the Scholar-President,” edited by Mario DiNunzio. Also, the 1944 film “Wilson,” starring Alexander Knox in the title role, is well worth watching.