“I am a very old man, and I have lived through almost the entire century,” wrote Isaiah Berlin in his 1994 essay, “A Message to the 21^st Century.”^[1] The 85-year old British political philosopher looked back at the carnage of the previous decades, and forward to the promise of a new millennium. The crimes of Genghis Khan “pale into insignificance next to the Russian Revolution and its aftermath: the oppression, torture, murder that can be laid at the doors of Lenin, Stalin, Hitler, Mao, Pol Pot.” And yet, with democracy spreading, “Great tyrannies are in ruins, or will be—even in China the day is not too distant.” The twenty-first century “can be only a better time for mankind than my terrible century has been.” However, he said, “I shall not see this brighter future, which I am convinced is coming.” Berlin died three years later in 1997.

Today, the philosopher’s dream of a better time for mankind may seem like a cruel illusion. The whole world appears to be on fire. After 2011, non-violent protests against Bashar al-Assad’s regime in Syria metastasized into a brutal civil war. In the catalytic heat of sectarian violence, Islamic State emerged as a hardened jihadist movement that swept from Syria into northern Iraq and declared a new caliphate. The overthrow of Muammar Gaddafi’s government in Libya in 2011 triggered a security vacuum and a fierce battle between rival militias to decide the succession.  During the summer of 2014, Israel launched a bloody intervention to suppress rocket fire from Gaza. Meanwhile, Russia clipped off the Crimean Peninsula from Ukraine, and fueled the secessionist violence in Eastern Ukraine. In 2012, Martin Dempsey, the Chairman of the U.S. Joint Chiefs of Staff said the world is, “more dangerous than it has ever been.”^[2]

And yet, from a different perspective, we could be witnessing the brighter future that Berlin foresaw. In his book The Better Angels of Our Nature, Steven Pinker collected a mountain of evidence showing that violence of all kinds has steadily declined over the centuries. Today, he wrote, “we may be living in the most peaceable era in our species’ existence.”^[3] Indeed, scholars broadly agree that global warfare has fallen significantly, ^[4] especially since 1945.^[5]

How can we reconcile these two viewpoints? Perhaps Pinker and his fellow professors are naïfs, fiddling with datasets while Aleppo burns. After all, U.S. President Abraham Lincoln appealed to the “better angels of our nature” in his First Inaugural Address in 1861—right before a horrific civil war killed 750,000 Americans.^[6]

Or, alternatively, perhaps the world really is getting more peaceful, but a shrieking kettle of hawks in the media and government blind us to the dove’s ascent.

The truth is that global violence has indeed declined, especially interstate wars fought between countries. But as the tide of conflict recedes, we are left with intractable civil wars that present a host of difficult challenges. There is a tale of two worlds. For interstate relations, it’s the best of times. For fragile countries, threatened by internal fracture, it may be the worst of times. And here the zones of peace and war collide. Countries may not fight each other directly, but they show few qualms about intervening in foreign internal conflicts. Indeed, civil wars have become the main arena for military competition between states. The world is not on fire. But even smoldering embers can suddenly alight.

The Best of Times

Let’s begin with the good news. Since World War II, there has been a striking decline in the level of interstate war, or fighting between the uniformed militaries of recognized countries. Of course, states have not suddenly become paragons of virtue. International politics remains a contact sport. Interstate wars do still happen, like the brutal Iran-Iraq War of the 1980s.

But these conflicts are now very rare. The chart below, from the National Academy of Sciences (via theAtlantic.com) reveals the decline of interstate war.^[7] Other data (here^[8] and here^[9]) show similar results.

World War II was a great crescendo of interstate violence that heralded what historian John Lewis Gaddis called “the long peace.”^[10] Great powers have not fought each other since the Korean War, over sixty years ago. In Western Europe, war used to be the sport of kings and despots. Now tourists can picnic safely on the Franco-German border.

Territorial expansion by force is no longer acceptable. Departments of war have been renamed as departments of defense. Empire building has gone out of fashion. For much of the world, war has shed its luster of glory. Theodore Roosevelt once declared: “no triumph of peace is quite so great as the supreme triumph of war.” But which leader of a developed democracy would repeat these words today?^[11]

There are many reasons for this happy tale of interstate peace, including memories of the world wars, nuclear deterrence, the spread of democracy, economic interdependence, and the creation of international institutions like the United Nations. The precise importance of each factor is much debated. But few can dispute that relations between countries have entered an era of almost unprecedented stability.

The Worst of Times

Now for the bad news: conflict still exists in the form of civil wars, or organized violence within the boundaries of a state. Of course, guerrilla warfare is nothing new. The term dates back to the Spanish rebels who battled against Napoleon over two centuries ago. But as interstate wars disappeared, insurgency has come to dominate the stage of global conflict. Today, almost nine-in-ten wars are civil wars.

The factors that produced interstate peace proved far less effective at stopping civil wars. Democracies may not fight each other but they do sometimes collapse into internal discord. Nuclear weapons may deter a foreign country from invading but they won’t deter an insurgency. Global interdependence may pacify relations between states but it can’t hold fragile countries together.

Meanwhile, the dynamics that increase vulnerability to civil war—poverty, foreign sanctuaries, mountainous and jungle terrain, and government incapacity—haven’t gone anywhere. And since 1945, three seismic events rippled through the international system, tearing apart fragile countries. First, the disintegration of the great European empires, and the emergence of dozens of brand new countries with weak institutions, provoked a wave of civil wars. Second, the end of the Cold War and the collapse of another empire, the Soviet Empire, produced a further spike in internal conflict. After the mid-1990s, the incidence of civil war fell back. But a third shock to the system—the Arab Spring in 2011—led to a new phase of violence in Libya, Syria, and elsewhere.

International terrorists also didn’t get the memo about the end of war. On 9/11, the United States was struck, not by a foreign army, but by a tiny band of nineteen men. This group bypassed America’s defenses like a virus and used the nation’s strength against itself, by turning aircraft into guided missiles. In recent years, the lines between terrorism and insurgency have blurred. Al Qaeda has evolved from a dedicated terrorist group into a loose network of militias that seek to govern territory in countries like Iraq, Syria, and Mali.

For the United States, foreign civil wars have become a major security issue, causing humanitarian crises, refugee flows, and terrorism. According to the 2002 National Security Strategy, “America is now threatened less by conquering states than we are by failing ones.”^[12]

The Eloi and the Morlock

In H.G. Wells’s classic novel The Time Machine, the hero travels far into the distant future and discovers that mankind has divided into two distinct classes: the Eloi, who live in luxury and peace above ground, and the primordial Morlocks, who toil underground and come out at night to feed on the Eloi.

In a sense, today’s world is one of Eloi and Morlocks, of countries living in interstate peace and societies riven by brutal civil wars. Occasionally, the Morlocks cross over from the zone of turmoil to the zone of harmony, like Al Qaeda emerging from Afghanistan to strike the United States on 9/11.

But more often the roles are reversed, and it’s the Eloi that feed on the Morlocks. Countries avoid interstate war but they display few inhibitions about wading into foreign internal conflicts. In other words, states rarely fight each other directly through conventional invasions. Instead, they compete indirectly through proxy wars, by backing rival insurgent or government factions with military aid, air strikes, or boots on the ground. Civil wars are now the primary battleground for military competition between countries. Like a recovering alcoholic stumbling upon a speakeasy, foreign civil wars are where countries rediscover their bad habits.

Proxy wars are nothing new. The Spanish Civil War (1936-1939) was a dress rehearsal for World War II, as Nazi Germany and fascist Italy backed the right-wing Spanish rebels, while the Soviet Union provided aid to the leftist regime in Madrid. During the Cold War, Washington regularly supported embattled regimes fighting insurgencies, for example, in South Vietnam, and also backed rebels groups in Afghanistan, Angola, Nicaragua, and elsewhere.

But foreign intervention in internal conflicts is on the rise. The number of internationalized civil wars recently reached its highest level since 1946.^[13] During the civil war in Iraq after 2003, Iran didn’t fight the United States directly.  Instead, Tehran trained and equipped Shiite militias that killed hundreds of American and allied troops.

Proxy war is also Russia’s main playbook of military intervention. In both Georgia in 2008 and Ukraine in 2014, Moscow backed rebel factions in civil conflicts on the Russian periphery.

Syria is the archetypal proxy war. Iran, Saudi Arabia, Russia, the United States, Britain, France, Turkey, and other countries, have provided aid to a diverse cast of factions on the ground.

The temptation to intervene and manipulate the course of a civil war is often hard to resist. Some states seek to end humanitarian suffering. More usually, they pursue their strategic interests. The supply of weapons, advisors, and troops can be covert and potentially deniable. And intervention may be dialed up or down as required to alter the outcome.

As we saw, democracy, nuclear weapons, changing global norms, and economic interdependence proved more effective at stopping wars between countries than within countries. And these dynamics also failed to prevent states from wading into foreign internal conflicts. Nuclear weapons can’t usually deter clandestine interference in a civil war. And to get around global norms against aggression, intervening troops become “volunteers,” soldiers “on leave,” or “little green men,” as Russian troops were described in Crimea.

Why does the rise of internationalized civil war matter? For one thing, these conflicts tend to be much bloodier than wars that remain a domestic affair.^[14] Furthermore, by meddling in civil wars, countries are playing with fire. Proxy wars could transmit conflict back to the interstate level—so the Eloi begin fighting each other directly again. In proxy conflicts, the patron usually remains aloof and the local ally has considerable autonomy. The ally may therefore act in unexpected ways, like shooting down the Malaysia Airlines jet in Eastern Ukraine. Today, internationalized civil wars could be the single greatest threat to global interstate peace.

A Better World

As the twentieth century wound down, Isaiah Berlin dreamed of a better future for mankind. In many respects, these hopes have transpired. We are fortunate enough to live in a time of unparalleled interstate peace. No one in 1945 could imagine that countries would almost give up waging aggressive conventional war. The whole world is not on fire. Indeed, the embers of conflict today pale next to the great infernos of the past.

But the near elimination of interstate war has left intractable civil wars as the major source of global conflict. And the same countries that abandoned interstate war are quite willing to meddle in internal disputes.

This is our world: Eloi and Morlock; peaceful and warlike; stable and unraveling. A world of messy internal conflicts is preferable to a world of ferocious interstate campaigns. But for the United States and its allies, managing internationalized civil wars presents a host of new challenges. Washington must entrench the sources of interstate peace and find new tools to dampen the flames of civil war. We live in a better time, if we can keep it.