On April 4, 1917, the U.S. Congress declared war on Germany. Two days before, President Woodrow Wilson addressed legislators, admitting that only they could plunge America into what amounted to a continental abattoir, daily consuming Europe’s best and brightest.

It was a fateful decision. The U.S. entered an imperial slugfest of little interest to Americans, killing 117,000 of America’s finest overseas and murdering civil liberties at home. Worse, Washington’s entry radically disrupted the continental balance of power, yielding a treaty that operated as a truce, turning into a far worse war only a generation hence. Although highly regarded by some academic histories, Wilson’s record puts him in competition for being the nation’s worst president.

The fuse that exploded Europe was lit in Sarajevo on June 28, 1914. The Serbian regime was awash in blood. In 1903, Col. Dragutin Dimitrijević, head of military intelligence, helped organize a military squad that assassinated Alexander I and his wife. The murders were particularly gruesome: the couple’s bodies were mutilated, disemboweled, and tossed into the garden. The result was dynastic change. The new regime hoped to destabilize Austro-Hungary and create a greater Serbia, or Yugoslavia.

In June 1914, Dimitrijević armed Serbian nationalist Gavrilo Princip, who targeted Austro-Hungarian Archduke Franz Ferdinand and his wife Sophie when they visited Sarajevo in Bosnia, which had been annexed by Austria-Hungary. Princip’s grievance against Ferdinand, the heir apparent to the throne, was that the latter was too pro-Slav; his plan to raise Slavs’ status within the Habsburg empire would defeat efforts to unite all Serbs. Princip declared at his trial, “I am a Yugoslav nationalist, aiming for the unification of all Yugoslavs, and I do not care what form of state, but it must be freed from Austria.”

It was freed, but at horrendous cost. During the war Serbia was occupied by the Austro-Hungarian army. Princip died in prison of tuberculosis and never saw the new state he was instrumental in creating. While in prison he spoke with psychiatrist Martin Pappenheim, who wrote that Princip believed a war was inevitable, so he “cannot feel himself responsible for the catastrophe.”

In fact, the war was not inevitable, but many policymakers thought so, leading some of them to believe that it might be best if it broke out then rather than later. The month that followed the assassination may be the most studied period of history. On July 28, Vienna declared war on Serbia.

The Austro-Hungarian government believed that it had to destroy a regime bent on the empire’s dissolution. Belgrade, however, was backed by Russia. Imperial Germany was treaty-bound to aid the Habsburgs. The Romanov dynasty was similarly allied with France, which was determined to regain territories seized by Germany in 1871 at the conclusion of the Franco-Prussian War.

Although Berlin possessed the continent’s finest army, winning a war on two fronts would be problematic. So Germany adopted the Schlieffen Plan, which required an early attack on France through Belgium while Russia still was mobilizing. The United Kingdom was concerned about maintaining the continental balance of power and created the so-called Triple Entente against Kaiser Wilhelm, who was a nephew of the British king and cousin of the Russian tsar. But the Asquith government refused to make its military commitment clear, hiding it from its own people and even its cabinet, as well as from Germany. Over time Japan, Italy, Bulgaria, Romania, and the Ottoman Empire joined the conflict, creating a global human slaughterhouse.

This was not a war between angels and demons, but of two sets of sometimes ugly authoritarians and militarists. Critics long have highlighted the mistakes and brutalities of the major Central Powers: Germany, Austro-Hungary, and the Ottoman Empire. Yet the former two were liberalizing though flawed constitutional orders. Imperial Germany had a larger franchise than imperial Britain, though the former’s government was responsible to a monarch who governed rather than an elected legislature backed by a mostly figurehead king, as in the UK. Both the Germans and Austro-Hungarians were too willing to jump off war’s precipice, but they were not alone in that proclivity.

On the other side, Serbia was a state sponsor of terrorism. Belgium was perhaps the world’s worst colonial administrator, presiding over mass murder in the Congo. The UK and France enforced authoritarian rule over hundreds of millions of Africans and Asians. France, which convulsed Europe in years of conflict during the Napoleonic wars, was a revanchist power determined to regain Lorraine and parts of Alsace lost to Germany in 1871, even if doing so required another continental war. Imperial Russia, the great anti-Semitic despotism, was ruled by a monarch determined to maintain absolutist control and resist liberal currents. Its later collapse was eagerly embraced by subject peoples, in the Baltics, Ukraine, and elsewhere, who fled its control. Italy joined the so-called Triple Entente after being promised territorial booty, Austro-Hungarian lands to be handed over with nary a nod to the wishes of their peoples.

None of this great tragedy concerned America in any important way. The British, however, launched a brilliant propaganda campaign in the U.S. using falsified German atrocities. (As a result, in World War II many people initially were skeptical of similar claims made about Berlin’s behavior, though in that case the stories did not adequately describe the horrors committed.) London borrowed heavily from U.S. banks, giving them a stake in a British victory. Activist, moralistic, imperialistic believers in the Social Gospel urged war to create a secular heaven. And Wilson, a man of boundless, hubristic ambition, was determined to transform the entire globe. He realized that only if he made America a belligerent would he be in a position to impose his views on the other warring powers.

His call to arms was a masterpiece of eloquent sophistry, which brought hardened, cynical solons to tears. His central casus belli was that the German government had “put aside all restraints of law or of humanity and use its submarines to sink every vessel that sought to approach either the ports of Great Britain and Ireland or the western coasts of Europe or any of the ports controlled by the enemies of Germany within the Mediterranean.”

There could be no more fraudulent justification for war. The UK used its dominant navy to impose an illegal “starvation blockade” on Germany — treating almost everything, even food for civilians, as contraband. This campaign killed hundreds of thousands of noncombatants as well as violated neutral, meaning American, rights. Yet Wilson’s protests to London were merely pro forma, lest he discomfit the British war effort.

In contrast, his complaints about the German U‑boat campaign were both vociferous and hypocritical. Submarines were ill-equipped to enforce a traditional blockade, which required stopping vessels to check and search for contraband. Worse, London secretly armed many such ships and ordered them to ram any U‑boat that attempted to comply with traditional practice by surfacing. Even passenger ships, like the Lusitania, were turned into reserve cruisers, armed, and used to transport munitions.

The latter was sunk in May 1915. It left New York with 139 Americans aboard — after the German government ran advertisements warning Americans not to travel on the ship. It was torpedoed 11 miles off the coast of Ireland; 1198 passengers died, including 128 Americans. But the Lusitania sank only after a second explosion, caused by ignition of the cargo of ammunition. After denying the obvious for decades, the British government admitted in 1982 that the wreck was too dangerous for divers to explore because ammunition littered the ship’s remains.

Wilson’s position was beyond outlandish. He believed that the presence of just one American should immunize a reserve military vessel of a belligerent power under orders to attack enemy submarines and carrying military contraband through a war zone. It was a nonsensical claim, understandable only as policy calculated to allow Washington to enter the war on behalf of the Allies. To make such a position the cause for war was murderous partisanship.

Berlin nevertheless drew back, hoping to avoid giving Wilson an excuse for war. As the exhausting conflict ground on, with blockade-induced malnutrition and even starvation stalking the home front, in early 1917 the German government announced the return to unrestricted U‑boat warfare. Hence Wilson’s plea to Congress.

“I was for a little while unable to believe that such things would in fact be done by any government that had hitherto subscribed to the humane practices of civilized nations,” he declared to the assembled members, after studiously ignoring the consequences of the British blockade. “The present German submarine warfare against commerce is a warfare against mankind,” he insisted, requiring the U.S. vindicate the most precious “human right” of traveling on belligerent ships carrying munitions through war zones.

Thus, he urged Congress to act:

With a profound sense of the solemn and even tragical character of the step I am taking and of the grave responsibilities which it involves, but in unhesitating obedience to what I deem my constitutional duty, I advise that the Congress declare the recent course of the Imperial German Government to be in fact nothing less than war against the Government and people of the United States; that it formally accept the status of belligerent which has thus been thrust upon it, and that it take immediate steps not only to put the country in a more thorough state of defense but also to exert all its power and employ all its resources to bring the Government of the German Empire to terms and end the war.

He admitted that he wanted to take peaceful America “into the most terrible and disastrous of all wars.” But, he contended,

the right is more precious than peace, and we shall fight for the things which we have always carried nearest our hearts — for democracy, for the right of those who submit to authority to have a voice in their own governments, for the rights and liberties of small nations, for a universal dominion of right by such a concert of free peoples as shall bring peace and safety to all nations and make the world itself at last free. To such a task we can dedicate our lives and our fortunes, everything that we are and everything that we have, with the pride of those who know that the day has come when America is privileged to spend her blood and her might for the principles that gave her birth and happiness and the peace which she has treasured. God helping her, she can do no other.

Of course, participation would do more than vindicate America pride in its own righteousness. Wilson went on to describe the wonders that would accrue to mankind as a result of the war: “We are at the beginning of an age in which it will be insisted that the same standards of conduct and of responsibility for wrong done shall be observed among nations and their governments that are observed among the individual citizens of civilized states.”

Alas, that isn’t how the conflict turned out.

As many as 21 million people died in the gloriously misnamed war to end war. Even more, perhaps 24 million, were injured, many grievously. Three monarchies, varying degrees of authoritarian but with hopes of continuing liberalization — Austria-Hungary, the Russian Empire, and Wilhelmine Germany — disappeared. The first was dismantled, the second was dissolved, and the third was wrecked by violent revolution and bloody civil war. The Ottoman Empire, long Europe’s “sick man,” also collapsed, adding to the continent’s violent chaos. From the resulting geopolitical miasma emerged communism, fascism, and Nazism.

The Versailles Treaty was supposed to institutionalize Wilson’s high-minded vision, but the haughty, sanctimonious, and vain Brahmin was easily and soundly outmaneuvered by the British and French prime ministers, David Lloyd George and Georges Clémenceau, respectively. They, along with Italy’s Prime Minister Vittorio Emanuele Orlando, greedily grabbed as much territory as possible as they plundered their helpless adversaries. The allies in the war that Wilson insisted was “for democracy, for the right of those who submit to authority to have a voice in their own governments” added to the major powers’ domains through so-called “mandates” from the newly created League of Nations.

The League was Wilson’s dream, which the cynical Europeans turned into a vehicle to protect their ill-gotten gains. But Wilson, who insisted on heading the American delegation and refused to include any leading Republicans, was unable to sell the mess of diplomatic pottage known as the Versailles Treaty on Capitol Hill. The Senate refused to ratify the pact, leaving the League essentially moribund at birth. After he suffered a stroke, his wife, Edith, effectively governed, and he lost all influence domestically and internationally.

Rather than negotiate with the losers, as at the end of the Napoleonic Wars, the Allies imposed what Germans called the Diktat. It was, but the Versailles Treaty actually fell between two stools. Although harsh, it was no Carthaginian peace, doing more to antagonize Germans than suppress their future potential. But the settlement also failed to conciliate; it blamed the entire conflict, which resulted from every belligerent choosing war for dubious reasons, on Germany — then a fledgling republic that had ceased fighting and ousted the Kaiser based on Wilson’s conciliatory “14 Points,” which he promised would guide the peace.

The treaty, the ultimate result of Wilson’s ill-judged decision to drag America into the war, was signed on June 28, 1919, five years to the day after Princip’s assassination. What amounted to a continental truce lasted little more than two decades. On September 1, 1939, Nazi Germany invaded Poland. The war spread around the globe, engulfing much of Europe and Asia, as well as America. By September 1945, when the fighting finally stopped, as many as 85 million people were dead, most of them civilians; multiple nations were in ruins, almost beyond recognition; Soviet communism had advanced into the heart of Europe, replacing totalitarianism with totalitarianism; war crimes had become widespread, sometimes committed even by the allies; and Hitler had unleashed the unimaginable Holocaust, a horrific attempt to destroy the Jewish people.

Such was the ultimate, though admittedly unintended, consequence, of Woodrow Wilson’s ill-considered call for war.

The lesson for today is clear: war always should be a last resort, limited to issues of extraordinary importance, and employed without illusions about the likely consequences. U.S. policymakers today blithely call for military action against China, Iran, North Korea, Russia, and other states, as if the only possible result would be success, glory, and peace. They should read a bit of history — especially Wilson’s glorious call to arms and the disaster that ultimately resulted.