By David Petraeus, Politico–

A little more than a century ago, at the dawn of the 20th century, Americans had reason to be hopeful. The great powers were at peace. Economic interdependence among nations was increasing. Miraculous new technologies were appearing with dizzying speed.

Yet this optimistic vision would soon fall to pieces. The first half of the 20th century would prove to be the bloodiest, most devastating period in human history, with the two most destructive wars in history; the worst economic collapse in history; and the near-takeover of the planet by an alliance of dictatorships responsible for the worst crimes against humanity in history.

The United States came of age as a world power amid the rubble left by this succession of calamities—and resolved, in the wake of the most devastating conflict the world has ever known, to try to prevent them from ever happening again.

To keep the peace, we led an effort to establish a system of global alliances and security commitments, underwritten by U.S. military power and the deployment of our forces to bases in Europe and Asia.

To create a foundation for prosperity, we put in place an open, free and rules-based international economic order intended to safeguard against the spiral of protectionism that produced the impoverishment and radicalization of the 1930s.

And to protect freedom here at home, we adopted a foreign policy that sought to protect and, where possible, promote freedom abroad, along with human rights and rule of law.

These were the bipartisan foundations for the international order that emerged after World War II. They were the product of American leadership, American power and American values. And while imperfect, on balance they succeeded.

The extent of that success can be seen when we compare the first half of the 20th century with the second half of that century—a period that witnessed the longest stretch without a great-power war in centuries; the most dramatic expansion of human prosperity in history; and the spread of democracy to every inhabited continent on the planet.

To borrow a phrase from the historian Robert Kagan, this is the world that America made.

It is also the world that, I fear, is now in danger of being unmade. The international order that America created is now under unprecedented threat from multiple directions, including by increasingly capable revisionist powers—that is, countries dissatisfied with the status quo, by Islamic extremist organizations that want to destroy our way of life, and by technologies and tactics that are reducing America’s capacity to defend ourselves and our interests.

As important as those various threats are, however, the world order has also been undermined by something perhaps even more pernicious—a loss of self-confidence, resolve and strategic clarity on America’s part about our vital interest in preserving and protecting the system we sacrificed so much to bring into being and have sacrificed so much to preserve.

The major challenge to the U.S.-led international order—the rise of a set of revisionist powers—is a development Americans have recognized but been reluctant to confront. Since the end of the Cold War, our hopeful assumption has been that mutual self-interest could provide a pathway for deepening partnership among the major powers, while globalization would gradually liberalize the internal politics of all countries.

What we have seen instead, unfortunately, is that, as certain countries have grown more powerful, so too has their desire to challenge at least some elements of the status quo, while domestically, their authoritarianism has grown both more entrenched and yet also more insecure. In particular, we see several countries—including China, Iran and Russia—now working to establish a kind of sphere of influence over their respective near-abroads, which include areas of vital strategic importance to the U.S., and where we have allies and partners to whom we are bound by shared interests and values.

To be sure, each of the revisionist powers requires a very different approach on America’s part. China, for example, is not just a rising great power and strategic competitor; it is also our No. 1 trading partner, and our relationship with it is the most important relationship in the world. In fact, in each case our relationship inevitably combines some aspects of intensifying rivalry with other aspects of shared interest, including the need to develop some concept of mutual restraint and respect. The challenge for the U.S. is to find the often elusive equilibrium—something that is likely to occur only if we combine hard-headed diplomacy with an equally hard-headed reinvestment in shoring up what has been a deteriorating balance of power.

A very different, far more radical revisionist force threatening the international order is Islamic extremism—the ideology that animates the Islamic State and Al Qaeda. The greatest weakness of Islamic extremism is also its greatest strength—which is its protean ability to exist and indeed thrive without inhabiting a conventional nation-state. What it lacks in traditional power terms, it compensates for in conviction, resilience, resourcefulness and ferocity. And in its hydra-like qualities, it is unlike any adversary we have faced before. What is still missing in many cases is a truly comprehensive approach to combating these extremists, though, to be fair, there has been progress in recent years developing an approach that enables local partners and allows us to achieve a sustainable strategy—with sustainability being measured in blood and treasure, and being an essential quality given the likely duration of the struggle in which we are engaged.

The defeat of Islamic extremist groups does, of course, require a vital military component. But even if we succeed militarily, as I believe we will, in metaphorically putting a stake through the heart of ISIS and its allies in Iraq and Syria, that success will be fleeting unless the underlying conflicts in those countries and the greater Middle East that enabled ISIS’ rise are addressed and resolved. We must also recognize that long-term success in this conflict requires that the ideology of Islamic extremism is itself discredited. And contending with the ideological caliphate in cyberspace will undoubtedly prove more challenging than taking away the rest of what is now a shrinking physical caliphate on the ground in Iraq and Syria.

Here I should note that our most important ally in this war is the overwhelming majority of Muslims who reject Al Qaeda, ISIS and their fanatical, barbaric worldview. Indeed, it is millions of Muslims who are fighting and dying in the greatest numbers on the front lines of this war—including Arab and Kurdish fighters bravely battling ISIS in Mosul; Gulf Arab forces taking the fight to Al Qaeda’s franchise in Yemen; Afghans courageously struggling against a resurgent Taliban and a nascent Islamic State affiliate; Somali forces confronting Al Shabab; and the Libyan elements that recently drove another Islamic State entity from the enclave it had seized on the North African coast.

We must also remember that Islamic extremists want to portray this fight as a clash of civilizations, with America at war against Islam. We must not let them do that; indeed, we must be very sensitive to actions that might give them ammunition to use in such an effort.

Compounding the danger posed by revisionist forces are technologies that are eroding America’s conventional military edge. In this respect, the wars of the post-9/11 period were, in some respects, a preview of the future. While the U.S. deployed forces into Iraq and Afghanistan that were superbly constructed for rapid decisive operations of the kind that we waged during the Gulf War in 1991, our adversaries responded with strategies that, for a fraction of the cost, nullified many of our advantages.

What Islamic extremists demonstrated through insurgency and terrorism, revisionist powers like China, Iran and Russia promise to take to a whole new level of sophistication. Among the fast-developing tools in their arsenals are anti-access area denial weapons that will complicate our ability to project power into vital regions and uphold our security commitments; increasingly complex cyberweapons for employment alone in attacks on infrastructure or in influence campaigns, or in supporting conventional and unconventional force operations, including so-called hybrid warfare; a renewed emphasis on nuclear weapons; and threats to U.S. primacy in space—a vital sanctuary for U.S. military power that is increasingly contested. These are all serious threats.

Despite these challenges, I believe America is in a commanding position to sustain and indeed bolster the international order that has served us—and, paradoxically, some of those seeking to change it—so well. We have an extraordinary network of partners who are stakeholders in the current order and can be mobilized far more effectively in its defense. Our economy remains the largest in the world and an engine of unsurpassed innovation. And as a result of America’s values—political pluralism, rule of law, a free and open society—we can recruit the best and the brightest from every corner of the planet, a strategic advantage that none of our competitors can match.

The paradox of the moment is that, just as the threats to the world order we created have grown ever more apparent, American resolve about its defense has become somewhat ambivalent.

To be clear, America cannot do everything, everywhere. Indeed, no one understands that better than the individual who was privileged to command the surge in Iraq and the surge in Afghanistan. But when the most egregious violations of the most basic principles of the international order we helped shape are tolerated or excused, that lack of action undermines the entire system—and is an invitation to further challenges.

Americans should not take the current international order for granted. It did not will itself into existence. We created it. Likewise, it is not naturally self-sustaining. We have sustained it. If we stop doing so, it will fray and, eventually, collapse.

This is precisely what some of our adversaries seek to encourage. Russian President Vladimir Putin, for instance, understands that while conventional aggression may occasionally enable Russia to grab a bit of land on its periphery, the real center of gravity is the political will of the major democratic powers to defend Euro-Atlantic institutions like NATO and the European Union. That is why Russia is tenaciously working to sow doubt about the legitimacy of these institutions and our entire democratic way of life. Perhaps because Russian civilization has a foot in the West, Russia as a great power has always been well-positioned—in a way that China and Iran are not—to wage ideological warfare that eats at the Euro-Atlantic world from within.

In this respect, repulsing this challenge is as much a test of America’s faith in our best traditions and values as it is of our military strength, though our military strength obviously is a crucial component of our national power, and does need shoring up.

I began this essay by evoking a dark time in the history of mankind. Yet it was only at our darkest hour in the 1940s that we summoned the imagination and determination to build the world order of which all of us here today have been the lucky heirs. Perhaps it is in the nature of humanity that, only when we came to grasp fully how bad things could be, were we capable of galvanizing ourselves to set them right.

That is also the great responsibility, and equally great opportunity, that those in positions of power have before them now—to conjure out of the accelerating crises and deepening challenges of the moment a world that is better than the one we inherited. And it is my hope that we will demonstrate the will and commit the resources needed to do just that.