Over the past several weeks, the war in Syria has crept back into the headlines, even competing with the drama and comedy of the Brett Kavanaugh hearings. The focus of attention is a potential humanitarian crisis and the prospect that the Assad regime might again use chemical weapons. Even President Donald Trump interrupted his normal Twitter flow to warn the Syrians, Russians, and Iranians not to “recklessly attack Idlib Province”—the last large pocket of Syrian resistance—lest “hundreds of thousands” of people be killed. “Don’t let that happen!” urged Trump.

The coalition backing Bashar al-Assad may be ruthless, but it isn’t reckless. Over the seven years of the Syrian conflict, it’s stuck to its guns, closely synchronized its diplomatic and military efforts, and, as the tide of the fighting has turned in its favor, adhered to a coherent campaign plan to reestablish control of the major population centers in the country. That campaign has largely centered on Syrian Highway 5, the major north-south line of communication in the east, connecting Aleppo in the north through Damascus to the southern border. The last link in this chain, still not reclaimed by Assad, runs through Idlib, which is also the last part of the U.N. “de-escalation zone”—a fiction that has considerably eased the Syrian government’s task.

The larger question is whether the conquest of Idlib would mark simply the end of the Syrian war and the survival of the Assad dynasty or whether it would signal the creation of a modern Iranzamin—loosely, “Greater Iran”—a sphere of influence reaching from the Caucasus and Central Asia to the Mediterranean, and what that might mean for the regional balance of power. The Idlib campaign also raises questions about past and present prospects for American interests and allies.

That the Assad regime survives at all is something of a wonder, after seven years of bloody war arising from relatively small and peaceful protests in January 2011. The process of survival, however, has cost Assad much of his autonomy, mortgaged to Russia and, especially, Iran. Indeed, what is emerging from Baghdad to Damascus is a kind of “Larger Lebanon,” where Tehran-backed Shia militias, created in the image of Hezbollah, hold the keys to the kingdoms.

To be sure, Syria and Iraq—where the intra-Shia struggle is just hitting high gear—are imperfect proxies for Iran, just as Hezbollah has been. And like the Lebanese original, which occasionally surprises even itself by lurching into open war against Israel, it seems quite likely that the rump regimes in Damascus and Baghdad will from time to time contravene Iranian direction in pursuit of their immediate interests. Yet from an Iranian perspective, these are not bugs but features of a model that has permitted Tehran to exert influence well beyond what might be feasible were its “revolutionary” posture to appear too Persian, too overtly imperial. And this “soft-power” approach has yielded hard-power benefits. Both Hezbollah fighters and, in recent years, Shia fighters from Iraq have served in Syria; these militia members have taken on some of the qualities of mercenaries, if not professionals.

The creation of Larger Lebanon already has had profound geopolitical effects in the Levant and the Gulf. It is making life even more miserable for Turkish strongman Recep Tayyip Erdogan, constraining his -neo-Ottoman dreams. Erdogan, not surprisingly, is sharing his pain with Europe, warning that the Idlib offensive will generate a new wave of refugees that he will be unable to control. There is some truth in this, although Erdogan’s current unhappiness may have more to do with the lack of respect shown him by Moscow and Tehran, and the collapsing Turkish lira, than sympathy for his “Syrian brothers,” as he calls them in his tweets. At the recent summit in Tehran with Vladimir Putin and Iranian leader Hassan Rouhani, Erdogan was very much the junior partner among the self-described “guarantor states” of the situation in Syria. Turkey may have a seat at this table, but Iran and Russia are in control of the menu. The Lebanonization of Syria and Iraq poses a strategic challenge to which Erdogan—who has been burning his bridges with Europe and the United States—has little response.

While the Turks have moved tanks to their border with Syria, the Russians have resumed and ratcheted up the intensity of airstrikes against southern Idlib. This repeats the pattern of the Syrian reconquest: initial Russian longer-range strikes to soften up opposition strongholds followed by Assad regime terror-bombing and then, cautiously, a mix of Syrian troops, Iranian Quds Force operatives and Shia militias, and a sprinkling of Russian forward observers and contract fighters. Because Idlib is the last redoubt of the opposition, it has received an influx of perhaps as many as a million refugees from other parts of western and southern Syria, and is defended by some 60,000 or more well-armed militia members of its own, including a number of hardcore jihadist units. The bombing effort is likely to be a patient one, perhaps punctuated by U.N.-moderated ceasefires that allow the attackers to regroup and the resistance to slip through the desert to the east or over the mountains to the north. The regime and its allies are more than willing to destroy Idlib to save it, but they are also sensitive to their own manpower limits.

It is also likely that Russia will remain an important player for the coming years, even as Iran tries to consolidate a Larger Lebanon. Not only do Russian aircraft, air defenses, and long-range artillery provide important tactical elements to the coalition, but its role in deterring American intervention would remain critical—even past the point at which Iran achieves a nuclear capability. Putin’s bold if small 2015 investment in Syria has thus far returned giant strategic profit, and Russia is now the sole broker for all interested parties, able to bargain with the United States, Saudi Arabia, and even Israel, as well as Iran and Assad. Experience probably has given Russian intelligence the best outside appreciation of the strengths and weaknesses of Iran’s militias and special assets, including covert operatives. After three years of steady but manageable effort, Russia shows no signs of exhaustion or overstretch and now enjoys a reputation for standing by its allies that resonates across the region.

This is precisely what the United States most lacks. The Trump administration, it must be said, has at least stopped the hemorrhaging of American strategic credit. This is surprising, considering the president’s oft-expressed desire to complete the withdrawals begun by his -predecessor. It also may not survive the inevitable departures of Defense secretary James Mattis and White House chief of staff John Kelly, whose Marine careers were defined by the wars of the Middle East. Whether Secretary of State Mike Pompeo could carry the load alone seems doubtful, and who can predict how a setback in this fall’s midterms—not to mention the denouement of the Mueller probe and the impeachment proceedings that might follow it—will further unhinge the president?

There is, however, the shadow of a Middle East strategy flickering on the White House walls. Recent news reports indicate that the administration intends to retain a residual U.S. force of several thousand in western Iraq, nominally to ensure the continued suppression of ISIS or its third-generation spawn. There are plans for staying in Afghanistan as well. These forces, along with the continued U.S. Navy patrolling of the Gulf and the Arabian Sea, do not themselves make for a policy of containing Iran, let alone a strategy of rollback; the military presence is necessary but hardly sufficient.

More telling is the administration’s patience with Saudi Arabia, including its tolerance of the very ugly Saudi war in Yemen. The larger strategic prize—and perhaps a light at the end of the current very dark and long tunnel—is the success of Crown Prince Mohammed bin Salman’s project of reform in Riyadh. That may be a long shot, but such is the degeneration of American influence in the Arab world since the retreat from Iraq. Indeed, the United States now finds itself in a position similar to where it was in the late 1940s, when Presidents Roosevelt and Truman lashed America’s Middle East hopes to the masts of Saudi Arabia and Israel.

Stepping back into the public square the other week, Barack Obama rightly described Trumpism as not the cause but the effect of the divisiveness and demagoguery besetting American political life over the past decade. He would know. And what is true domestically is true internationally, too. Even more so: “Iraq Derangement Syndrome” has been more virulent and long-lived than hatred of our last or our current president, and it certainly will not be cured by a change of administration.

The dismemberment of Idlib will create not only a humanitarian disaster but a strategic one for the United States, its interests, and its allies, in Europe and well as the Middle East proper. Donald Trump is right to scream, “Don’t let that happen!” But until he, or we, are prepared to do something beyond appealing to the tender heart of Vladimir Putin, it’s going to happen. And happen again.