The nationwide release in January of Peter Jackson’s World War I documentary “They Shall Not Grow Old” does a great service to us and to history by re-humanizing the men who waged the Great War—reminding us that they were not wordless, colorless two-dimensional figures, but rather flesh and bone. More than that, Jackson’s work—the product of years of digitally remastering, colorizing and adding sound to film stored at Britain’s Imperial War Museum—gives us an opportunity to explore the many lessons and leftovers of what an earlier generation naively called “the war that will end war.”

INOCULATIONS

A first lesson relates to the years leading up to the war: Trade and globalization are not failsafe inoculations against war.

On the eve of World War I, as Niall Ferguson writes, “The world had been economically integrated in a way never seen before.” Rail lines, shipping and telegraphs “shrank the world.” Ocean-freight costs fell by a third between 1870 and 1910. Labor was flowing freely across borders.

Iron-ore imports from France to Germany grew 60-fold in the 13 years before the Great War. In 1914, Britain accounted for more than 14 percent of Germany’s exports. British exports to continental Europe swelled by 88 percent between 1900 and 1913, German exports to Britain by 69 percent. Total U.S. trade with what would become the Central Powers increased 41 percent between 1908 and 1913. This was “the first globalization,” Ferguson explains. Many believed such trade linkages made war unthinkable—then came the summer of 1914.

Trade between nations is an inherently good thing, but those who assure us America and China could never go to war because of trade linkages ignore what happened in 1914. Annual U.S.-China trade is more than $635 billion. The value of trade between the two economic giants jumped 65 percent between 2007 and 2017. As historian Robert Kagan warns, “The United States and China are no more dependent on each other’s economies today than were Great Britain and Germany before World War I.”

TREATIES

A second lesson relates to the heady and hopeful years following the war. Treaties are not enough to keep the peace or protect U.S. interests. “In time of crises,” President Theodore Roosevelt concluded in 1914, “peace treaties are worthless.” He made that case repeatedly during the war, pointing out the “utter worthlessness of treaties” and how they “offer not even the smallest protection against such disasters.”

These words come from a man who believed in diplomacy, who negotiated treaties that staved off and ended wars in Europe, Africa and Asia, who earned a Nobel Peace Prize. Yet years of experience taught him that “diplomacy is utterly useless where there is no force behind it.”

President Woodrow Wilson came to this realization far too late. It pays to recall that when German submarines began attacking merchant ships, Wilson vowed to hold the Kaiser to “strict accountability.” Yet after Americans were killed aboard the Falaba, Gulflight, Arabic and Lusitania, he responded by writing letters and holding to his pledge that America would remain “neutral in fact as well as in name.”

TR’s assessment about the connection between diplomacy and force remains unchanged a century later because man’s nature remains unchanged. Treaties are only as good as the character of the governments that sign them. This should give us pause in our dealings with Putin’s Russia, China’s business-suit autocrats and totalitarian North Korea. Bad guys do bad things. Treaties, UN resolutions and strongly worded letters seldom correct, let alone prevent, bad behavior.

PREPAREDNESS

However, there are actions that can help improve the ecosystem in which treaties live and help prevent bad behavior—or at least limit its effects. That brings us to a third lesson of the Great War: Military preparedness helps keep the peace, while unpreparedness invites danger.

America was woefully ill-prepared in 1914. “Our navy is lamentably short in many different material directions. There is actually but one torpedo for each torpedo tube,” TR lamented. “For nearly two years, there has been no fleet maneuvering.”

TR understood that being prepared for war is the best way to prevent war. “The United States has never once suffered harm because of preparation for war,” he explained. “But we have suffered incalculable harm, again and again, from a foolish failure to prepare for war.”Moreover, being prepared for war is far less costly than waging war. In the eight years before World War I, America devoted an average of 0.7 percent of GDP to defense. During the war, America expended 16 percent of GDP on defense and sacrificed 116,516 dead—in 503 days of combat. Indeed, the war was staggering in its totality and lethality. Although the war was romanticized when the guns thundered to life, those who survived the trenches knew it was more apocalyptic than romantic: Like Revelation’s Four Horsemen, it brought conflict (28 nations were engaged), famine (Belgium starved; Germany survived on turnips), death (10 million soldiers and 6 million civilians died) and pestilence (the 1918-19 influenza pandemic claimed 50 million people). Indeed, Jackson’s documentary reminds us there was nothing romantic about the Great War. “What’s it like up there?” a wide-eyed enlistee headed for the front asks a battle-weary soldier headed the other direction. The veteran’s answer: “Bloody awful.”

Sadly, America reverted to its old ways after the war. In the 1930s, the United States spent an average of just 1.1 percent of GDP on defense annually—then came a day of infamy. The U.S. diverted an average of 27 percent of GDP to defense after Pearl Harbor—and lost 405,399 lives defeating the Axis.

Recognizing that it’s wiser to make the relatively small investments necessary to deter war than to expend enormous amounts of wealth and human life to wage war, Americans spent an average of 7 percent of GDP on defense annually during the Cold War to keep the Red Army at bay. It worked. Regrettably, Washington abandoned that proven approach and instead engaged in a bipartisan gamble known as sequestration, slashing defense spending from 4.7 percent of GDP in 2009 to 3.2 percent by 2016. Measured in constant dollars, defense spending fell by nearly one-fourth between 2010 and 2015. These cuts might have made sense if peace were breaking out. But with Beijing annexing the South China Sea, Moscow assaulting Georgia and Ukraine, Pyongyang fielding long-range missilery, Tehran spreading its malign influence across the Middle East, Russia’s military outlays jumping 125 percent since 2006 and China’s 190 percent since 2008, we know the very opposite to be true.

Recent defense budgets have ended sequestration’s maiming of the military, but as then-Defense Secretary James Mattis concluded in 2017, “It took us years to get into this situation. It will require years of stable budgets and increased funding to get out of it.”

In a broken world crammed full of broken nations led by broken men, there isn’t a viable alternative to deterrence, as underscored by the disaster that followed the Great War. However, the deterrent strength that helps prevent great-power war must be paired with clarity of intent, as underscored by the disaster leading up to the Great War.

A common refrain is that Europe’s arms race triggered the Great War. But if arms races caused war, then a) there shouldn’t have been a World War II, since the Allies allowed their arsenals to atrophy after World War I, and b) there should have been a World War III, since Washington and Moscow engaged in a massive arms race after World War II. The reality is that miscalculation lit the fuse of World War I. The antidote is clarity plus strength. Arms alone aren’t enough to deter war. The great powers were indeed armed to the teeth in 1914. But since they weren’t clear about their treaty commitments, a small crisis on the fringes of Europe mushroomed into a worldwide war. Nor is clarity alone enough to deter war. Wilson’s words to the Kaiser were clear, but America lacked the military strength to bolster those words.

The men who crafted the West’s post-World War II blueprint applied the clarity-plus-strength model. But with America’s words during the Trump administration doing more to worry allies than reassure them—and America’s deterrent strength whittled away during the Obama administration—Washington has abandoned that blueprint.

LEFTOVERS

Like landmines scattered along the Western Front, the war’s leftovers remain strewn across the world.

Dynamite

In his war message, Wilson committed America to fight for “the rights of nations great and small…to choose their way of life.” A year later, he added: “Self-determination is…an imperative principle of actions which statesmen will henceforth ignore at their peril.”

Wilson’s secretary of state, Robert Lansing, called it “a phrase loaded with dynamite…It will, I fear, cost thousands of lives.” He wondered, “When the president talks of ‘self-determination’ what unit does he have in mind…a race, or a territorial area, or a community? Without a definite unit that is practical, application of this principle is dangerous to peace and stability.”

Wilson may have sensed the tides of history carrying humanity toward decentralization, but Lansing’s instincts were right: In 1900, there were 57 independent countries. Today, there are nearly 200. Many of them came into existence through wars of self-determination; many of those wars triggered other wars. Consider the UN’s newest member, South Sudan, which seceded from Sudan and is now in the midst of a fight that could further divide the country; or Kosovo, which cut itself away from Serbia and is now dealing with a Serbian enclave that wants to cut itself away from Kosovo; or Ukraine, where Moscow wrapped its annexation of Crimea in the blanket of self-determination; or the Kurds of Iraq and Catalonians of Spain, who want to turn their autonomy into independence. The list goes on, just as Lansing feared. “What a calamity that the phrase was ever uttered,” he wrote as he contemplated where Wilson’s promise of self-determination would lead.

Visions

Wilson’s defenders would counter that he and his Fourteen Points were so visionary that the world was not ready to embrace them in 1919, and there’s some truth to this.

Wilson envisioned “a partnership of democratic nations,” “open covenants…openly arrived at,” “freedom of navigation upon the seas,” lower trade barriers, “impartial adjustment of all colonial claims,” borders based on “recognizable lines of nationality”—all undergirded by a “general association of nations.”

These concepts speak to the great sweep of Wilson’s vision. Much of this served as the foundation for the liberal order Franklin Roosevelt and Winston Churchill began building a generation later.

Leninism

“They turned upon Russia the most grisly of weapons,” Churchill wrote: “Lenin in a sealed truck like a plague bacillus from Switzerland to Russia.” Russia and the world would never be the same.

The immediate effect was exactly what Germany desired: Lenin’s revolution knocked Russia out of the war. But there were far more lasting consequences.

To build his workers’ paradise, Lenin murdered some 4 million. Many others would embrace his methods. The Black Book of Communism catalogues a “multitude of crimes…against individual human beings…world civilization and national cultures” spawned by communism. The book estimates the Soviet state murdered 20 million of its subjects; China 65 million; North Korea 2 million; Cambodia 2 million; Vietnam 1 million. Communist regimes in Africa, Afghanistan, Eastern Europe and Latin America also learned Lenin’s ways of mass-murder on an industrial scale. Lenin’s victims were every creed, every color and every race. They died on nearly every continent. And with Leninist regimes still in power in certain corners of the earth, Lenin’s reach and toll are now seeping into a second century.

A revolution to topple the decaying czarist regime may have been inevitable in 1918, but it didn’t have to be a Leninist revolution. The fact that it was made all the difference.

Organ Failure

There was hope after the war that nations might begin solving disputes through international conferences and international organizations. Hence the flurry of postwar summits, treaties and pacts: The Versailles Peace Conference officially ended the war, midwifed the League of Nations, disarmed Germany and redrew the map of Europe. The Washington Conference yielded the Nine-Power Treaty, which guaranteed the independence of China; the Five-Power Treaty, which established limits on the number and tonnage of ships America, Britain, Japan, France and Italy could maintain; and the Four-Power Pact, under which America, Britain, France and Japan agreed to respect one another's possessions in the Pacific. The Kellogg-Briand Pact even outlawed war. Sixty-two nations signed the treaty, but there were no real enforcement measures.

That was true of all those well-intentioned efforts. Thus, Hitler’s Germany rearmed and re-redrew Europe’s map; Tojo’s Japan used naval power to plunder China and attack British, French and American territories; Japan, Germany and Italy—original signatories of the Kellogg-Briand Pact—attacked most of the other original signatories; and the League of Nations failed to stop aggressor nations from violating treaties and brutalizing their neighbors.

Like the League, the UN has proven unable to keep the peace or maintain order. This is partly a function of systemic shortcomings within these manmade institutions, partly a function of humanity’s unwillingness to engage in the tradeoffs necessary to work toward peace between nations.

This is not to succumb to fatalism or to suggest that we wash our hands of the messiness of the world. Rather, it’s a reminder that we must deal with the world as it is and fashion practical solutions to protect innocents and maintain some semblance of order. For a century, international bodies—first the League of Nations, then the United Nations—have failed to reach that rather low bar, which explains the growing support for a bona fide global partnership of democratic nations.

Yet America appears increasingly unwilling to lead such an effort. Both the visionary idealism of Wilson and the hard-nosed realism of TR—which, when mixed together in the right proportions, served as the cement for the liberal international order America began building after World War II—have been replaced by inward-looking promises to focus on nation-building at home and put America first. This inward turn serves neither the national interest nor the interest of international order, which is very much in the national interest.

“It has been said that the United States never learns by experience, but only by disaster,” TR observed during the Great War. “Such method of education may at times prove costly.”

A longer version of this essay appeared in the autumn 2018 issue of Providence.