For several years, there has been a significant shift underway in U.S. strategy toward the Middle East, where Washington has consistently sought to avoid combat. The United States is now compelled to seek accommodation with Turkey, a regional power in its own right, based on terms that are geopolitically necessary for both. Their relationship has been turbulent, and while it may continue to be so for a while, it will decline. Their accommodation has nothing to do with mutual affection but rather with mutual necessity. The Turkish incursion into Syria and the U.S. response are part of this adjustment, one that has global origins and regional consequences.

Similarly, the U.S. decision to step aside as Turkey undertook an incursion in northeastern Syria has a geopolitical and strategic origin. The strategic origin is a clash between elements of the Defense Department and the president. The defense community has been shaped by a war that has been underway since 2001. During what is called the Long War, the U.S. has created an alliance structure of various national and subnational groups. Yet the region is still on uneven footing. The Iranians have extended a sphere of influence westward. Iraq is in chaos. The Yemeni civil war still rages, and the original Syrian war has ended, in a very Middle Eastern fashion, indecisively.

A generation of military and defense thinkers have matured fighting wars in the Middle East. The Long War has been their career. Several generations spent their careers expecting Soviet tanks to surge into the Fulda Gap. Cold Warriors believed a world without the Cold War was unthinkable. The same can be said for those shaped by Middle Eastern wars. For the Cold War generation, the NATO alliance was the foundation of their thinking. So too for the Sandbox generation, those whose careers were spent rotating into Iraq or Afghanistan or some other place, the alliances formed and the enemies fought seemed eternal. The idea that the world had moved on, and that Fulda and NATO were less important, was emotionally inconceivable. Any shift in focus and alliance structure was seen as a betrayal.

After the Cold War ended, George H.W. Bush made the decision to stand down the 24-hour B-52 air deployments in the north that were waiting for a Soviet attack. The reality had changed, and Bush made the decision a year after the Eastern European collapse began. He made it early on Sept. 21, 1991, after the Wall came down but before the Soviet Union collapsed. It was a controversial decision. I knew some serious people who thought that we should be open to the possibility that the collapse in Eastern Europe was merely a cover for a Soviet attack and were extremely agitated over the B-52 stand-down.

It is difficult to accept that an era has passed into history. Those who were shaped by that era, cling, through a combination of alarm and nostalgia, to the things that reverberate through their minds. Some (though not Europeans) spoke of a betrayal of Europe, and others deeply regretted that the weapons they had worked so hard to perfect and the strategy and tactics that had emerged over decades would never be tried.

The same has happened in different ways in the Middle East. The almost 20-year deployment has forged patterns of behavior, expectations and obligations not only among individuals but more institutionally throughout the armed forces. But the mission has changed. For now, the Islamic State is vastly diminished, as is al-Qaida. The Sunni rising in Iraq has ended, and even the Syrian civil war is not what it once was. A war against Iran has not begun, may not happen at all, and would not resemble the wars that have been fought in the region hitherto.

This inevitably generates a strategic re-evaluation, which begins by accepting that the prior era is gone. It was wrenching to shift from World War II to the Cold War and from the Cold War to a world that many believed had transcended war, and then to discover that war was suspended and has now resumed. War and strategy pretend to be coolly disengaged, but they are passionate undertakings that don’t readily take to fundamental change. But after the 18 years of war, two things have become clear. The first is that the modest objective of disrupting terrorism has been achieved, and the second is that the ultimate goal of creating something approaching liberal democracies was never really possible.

Consistency

The world has changed greatly since 2001. China has emerged as a major power, and Russia has become more active. Iran, not Sunni jihadists, has become the main challenge in the Middle East and the structure of alliances needed to deal with this has changed radically since Desert Storm and Iraqi Freedom. In addition, the alliances have changed in terms of capability. The massive deployments in the Middle East have ended, but some troops remain there, and to a section of the American military, the jihadist war remains at the center of their thinking. To them, the alliances created over the past 18 years remain as critical as Belgium’s air force had been during the Cold War.

There is another, increasingly powerful faction in the United States that sees the Middle East as a secondary interest. In many instances, they include Iran in this. This faction sees China or Russia (or both) as the fundamental challenger to the U.S. Its members see the Middle East as a pointless diversion and a drain of American resources.

For them, bringing the conflict to a conclusion was critical. Those who made their careers in this war and in its alliances were appalled. The view of President Donald Trump has been consistent. In general, he thought that the use of military force anywhere must be the exception rather than the rule. He declined to begin combat in North Korea. He did not attack Iran after it shot down an American drone or after it seized oil tankers in the Strait of Hormuz. After the attack on the Saudi oil facility, he increased Saudi air defenses but refused offensive actions against the Iranians.

Given the shift in American strategy, three missions emerge. The first is the containment of China. The second is the containment of Russia. The third is the containment of Iran. In the case of China, the alliance structure required by the United States is primarily the archipelago stretching from Japan to Indonesia and Singapore – and including South Korea. In dealing with Russia, there are two interests. One is the North European Plain; the other is the Black Sea. Poland is the American ally in the north, Romania in the south. But the inclusion of Turkey in this framework would strengthen the anti-Russia framework. In addition, it would provide a significant counter to Iranian expansion.

Turkey’s importance is clear. It is courted by both Russia and Iran. Turkey is not the country it was a decade ago. Its economy surged and then went into crisis. It has passed through an attempted coup, and internal stress has been massive. But such crises are common in emerging powers. The U.S. had a civil war in the 1860s but by 1900 was producing half of the manufactured goods in the world while boasting a navy second only to the British. Internal crises do not necessarily mean national decline. They can mean strategic emergence.

Turkey’s alignment with Iran and Russia is always tense. Iran and Russia have at various times waged war with Turkey and have consistently seen Iraq as a threat. For the moment, both have other interests and Turkey is prepared to work with them. But Turkey is well aware of history. It is also aware that the U.S. guaranteed Turkish sovereignty in the face of Soviet threats in the Cold War, and that the U.S., unlike Russia and Iran, has no territorial ambitions or needs in Turkey. Already allied through NATO and historical bilateral ties, a relationship with Turkey is in the American interest because it creates a structure that threatens Iran’s line to the Mediterranean and compliments the Romanian-U.S. Black Sea alliance. The U.S. and Turkey are also hostile to the Syrian government. For Turkey, in the long term, Russia and Iran are unpredictable, and they can threaten Turkey when they work together. The American interest in an independent Turkey that blocks Russia and Iran coincides with long-term Turkish interests.

Enter the Kurds

This is where the Kurds come into the equation. Eastern Turkey is Kurdish, and maintaining stability there is a geopolitical imperative for Ankara. Elements of Turkey’s Kurds, grouped around the Kurdistan Workers’ Party, or PKK, have carried out militant attacks. Therefore it is in Turkey’s interest to clear its immediate frontiers from a Kurdish threat. The United States has no overriding interest in doing so and, indeed, has worked together with the Kurds in Iraq and Syria. But for the Turks, having Kurds on their border is an unpredictable threat. American dependency on the Kurds declines as U.S. involvement in the Middle East declines. Turkey becomes much more important to the United States in relation to Iran than the Kurds.

Trump clearly feels that the wars in the Middle East must be wound down and that a relationship with Turkey is critical. The faction that is still focused on the Middle East sees this as a fundamental betrayal of the Kurds. Foreign policy is a ruthless and unsentimental process. The Kurds want to establish a Kurdish nation. The U.S. can’t and doesn’t back that. On occasion, the U.S. will join in a mutually advantageous alliance with the Kurds to achieve certain common goals. But feelings aside, the U.S. has geopolitical interests that sometimes include the Kurds and sometimes don’t – and the same can be said of the Kurds.

At the moment, the issue is not al-Qaida but China and Russia, and Turkey is critical to the U.S. for Russia. The U.S. is critical for Turkey as well, but it cannot simply fall into American arms. It has grown too powerful in the region for that, and it has time to do it right. So Trump’s actions on the Syrian border will result in President Recep Tayyip Erdogan’s visit to Washington and, in due course, a realignment in the region between the global power and the regional power.