President Trump’s decision to give a de facto green light to a Turkish invasion of northern Syria continues to engender understandable criticism. Lost amidst this furor are several relevant facts: the modest U.S. military presence was inadequate to achieve any of the very ambitious objectives that the missions’ supporters imagined it could. As we wrote elsewhere, these troops were not going to “force Assad to yield, ensure free elections, limit Russian influence, oust Iranian forces, prevent an Islamic State revival, or protect the Kurds.”

A separate point concerns the conflicts and contradictions underlying U.S. policy in Syria, and indeed throughout the greater Middle East, which have been laid bare in recent weeks. These problems have been compounded by a tendency among the foreign policy elite to conflate U.S. obligations to formal treaty allies with those implied or inferred toward temporary partners of convenience. As we explain in this article at War on the Rocks:

The Syrian Kurds used Americans much as the Americans used them, to battle a common foe. Washington provided military assistance to a group which faced extinction should the Islamic State triumph. Importantly, the U.S. commitment was against ISIS, not Syria, Iran, Russia, or Turkey. And there was no formal alliance, no treaty ratified by the Senate, and no public debate. There wasn’t even legal authority for the deployment, let alone a commitment to go to war on behalf of the Kurds. The U.S. mission in Syria cannot reasonably be counted as legitimate under either the 2001 or 2002 versions of the Authorization for Use of Military Force — though the Obama and now Trump administrations have tried.

On the other hand, the United States and Turkey have been formal treaty allies for almost seven decades. Ankara has not been a very good ally of late, but it remains a member in good standing in the NATO alliance. Long ago, the U.S. Senate ratified Turkey’s inclusion in that treaty, which includes a promise to act collectively in defense of individual members…

And U.S. officials knew that Ankara viewed Washington’s relationship with the Syrian Kurds as a serious, even existential, threat. The issue is not whether U.S. officials believed Turkey’s claims. In fact, the connections between the Kurdish-dominated People’s Protection Units, or YPG, in Syria, with the Kurdistan Worker’s Party, or PKK, in Turkey are real, but seem unlikely to threaten the integrity of the Turkish state. Nevertheless, Ankara, not America, makes decisions on Turkey’s security. Turkish officials repeatedly and loudly informed Washington of their concerns.

But U.S. policymakers routinely ignored these protests, and Turkey interpreted this reaction as tantamount to abandonment. In other words, though nothing can justify attacks on innocent civilians, “Turkey’s behavior was motivated, in part, by a desire to resolve a security problem that it sees the United States as having made worse.”

The article goes on to explain how these sorts of problems are endemic when the United States allies or partners with nations or non-state actors that have a history of enmity toward one another. And when the strategic circumstances that occasioned the security commitment change — as, for example, at the end of the Cold War, or when the proximate threat posed by the Islamic State (though long exaggerated) abated — then U.S. policymakers should revisit those relationships, and strive to prevent the sorts of tragedies that are now playing out in northern Syria.

Read the whole thing here.