Almost five years after President Obama withdrew the last American troops from Iraq, the tidal waves of the war in that country are pulling him back in.

Obama has been resisting those tides, at first restricting himself to mounting airstrikes against ISIS, then sending trainers, then special operations forces initially as “advisers,” but increasingly in roles that place them on the edge of combat—and, very soon now, in the thick of it.

Secretary of Defense Ash Carter announced this week that, for the coming battle to liberate Mosul, another 217 troops will be sent to Iraq (bringing the total to 4,087, not counting the few-hundred special operations forces); that they’ll move to the front lines with Iraqi soldiers on the battalion level (before, American troops tended to stay on bases); that they and the Iraqis will be supported in the air not only by drones and fighter jets but also by Apache helicopters—and on the ground by the new High Mobility Artillery Rocket Systems, which can fire waves of rockets or missiles from long range with great accuracy. (One military source on the ground says that these advanced artillery rockets have been pounding ISIS targets for a couple of weeks now.)

In short, we are going to war in Iraq against ISIS. It’s not going to be like George W. Bush’s 2003 invasion of Iraq: It will involve about 5,000 U.S. troops, not 150,000; and local forces—Iraqi soldiers, Kurdish peshmerga, and various militias—will be in the lead. But the United States will be directly involved in the fighting and quite possibly the dying. And although Carter and other senior officials say the U.S.’s mission isn’t changing it’s clear that, by any reasonable definition of “mission” and “changing,” it is.

What’s going on with U.S. forces in Iraq, in fact, is a living, looming case study in “mission creep.”

Several times in the past couple years, Obama has resisted the pressures of mission creep, saying that, yes, U.S. ground forces would push ISIS out of Mosul in reasonably short order, but then what? Unless Iraqi troops came in to restore order and keep ISIS out, we’ll be stuck there for years or decades.

The good news is that, over the past several months, a joint force of American special-ops officers and Italian carabinieri have been training Iraqi military-police units to do just that. They’ve done it, to some degree, after Iraqi troops and militias have retaken Tikrit and Ramadi. And they’re preparing to do it, on what would be a much larger scale, in Mosul (which is four to five times larger than those other cities).

So, at least in theory, that meets one of Obama’s conditions for dropping his resistance to getting U.S. troops more involved in an offensive military action.

But he’s also cited another reason for restraint: There’s no point in throwing American troops into this conflict without a decent prospect for a political solution. Specifically, as long as Iraq’s Shiite-led government doesn’t share power with the Sunnis, ISIS (or jihadist organizations like ISIS) can’t be crushed. The Baghdad government’s oppressive policies and corrupt practices might not have caused the rise of ISIS, but they’ve helped sustain it and legitimized the grievances that ISIS has exploited, encouraging even many moderate Sunnis to tolerate—or at least not rebel against—the presence of ISIS as the lesser of two evils.

Prime Minister Haider al-Abadi has more inclusive inclinations than his predecessor, Nouri al-Maliki. And the American commanders in Iraq have done much to reinforce these tendencies, for instance paying the Kurdish peshmerga and the anti-ISIS Sunni tribal fighters through the Baghdad treasury—and thus building a sense of loyalty to and from the government—rather than giving them cash directly, as was done during the tribal co-optations of 2007 (as had to be done, since Maliki wasn’t willing to be the conduit). Another hopeful sign: The U.S. commander leading this tribal coordination is Lt. Gen. Sean MacFarland, who, as a colonel back in 2006, organized the Anbar Awakening, the first (and, for a while, pivotal) campaign in which Sunni militias cooperated with U.S. troops to beat back al-Qaida. When it comes to melding tribal politics and military entities in western Iraq, MacFarland has no equal.

Still, sectarian favoritism still dominates Iraqi politics; corruption is rife; and Sunnis have yet to be shown a compelling reason to turn against ISIS, and thus tilt in favor of the government, in large numbers.

The U.S. and its allies may succeed in pushing ISIS out of Mosul, and that’s a good thing on many levels. But as a report this week by the Soufan Group puts it, “Even the most decisive military victory in Mosul will be short-lived if the factors that gave rise to the current violence and turmoil remain unresolved. … Without true political and social reform, the battle against [ISIS] in Mosul will be repeated elsewhere in a few years.” The report adds: “Unfortunately, reform of this scale in a traumatized and divided nation is as unlikely as it is vital.”

This is what Obama and many of his top officials and generals have meant when they say (as they have repeatedly) that we can’t kill our way out of this crisis. Yet this is what they are preparing to do anyway, because, like a carpenter who tends to solve every problem with a hammer and some nails, it’s what they do best.

Which isn’t to deprecate hammers and nails; sometimes they’re precisely what’s needed to do the job. Obama has long realized this, but he has a tendency—often historically justified—to let others do the dangerous carpentry when America’s vital interests aren’t at stake. And so, when he first declared that ISIS must be destroyed, he tried to assemble a coalition of Muslim nations and militias to do the fighting on the ground, offering to support their effort with America’s combat specialties—precision airstrikes, intelligence, and logistical support. But it turned out there was no such coalition to be had, as its logical members—which included just about every nation and militia in the region—feared and loathed one another at least as much as they feared and loathed ISIS (a fact that ISIS has shrewdly exploited).

Yet Obama had declared, and has continued to declare, that ISIS must be destroyed—and so he stepped up the airstrikes (even though he knew that airstrikes alone can’t win a war), and he sought partners where he could find them, most notably the Kurds (even though he knew they would fight only to defend their own turf, not go chasing jihadists all over the country). And so he moved, incrementally but inextricably, toward deepening America’s involvement, widening its stake, heightening its risk.

Secretary Carter, who has long pushed for a more aggressive stance against ISIS, insisted in his speech that our new steps—the extra troops, the embedding with Iraqi battalions, the deployment of Apache helicopters and long-range accurate artillery pieces—don’t constitute a new strategy. Officials in the White House and the State Department say the same thing: What we’re about to do merely continues the strategy we’ve been pursuing all along.

This would be true only if the U.S. strategy were defined as “defeating and destroying ISIS,” in which case any action, along a continuum from Obama’s policies of the last two years to dropping tactical nuclear weapons, could be justified as part and parcel of the same strategy. But “strategy” isn’t such a broad term, and a military strategy must set down not only the goal of an operation but also the means to achieve the goal—the costs one is willing to bear and not bear, the risks one is willing to take and not take.

In that sense, the only meaningful sense, U.S. strategy in Iraq is on the verge of changing—and this is happening as a result of decisions that President Obama has made.

Whether Obama sees it this way is another matter. I suspect he does: This is a president who has something of an allergy to escalation, especially if it seems to be spiraling out of control. But I also suspect he thinks he can maintain his grip on the spiral. As I’ve written elsewhere, Obama has a keen legal mind, which serves him and his country well when he pokes holes in specious arguments for risky policies. But it also enables him to rationalize his own porous positions: for instance, that conducting joint raids falls in the category of “advise and assist,” or that special operations forces don’t constitute “boots on the ground.”

My guess is that Obama really won’t push U.S. ground forces beyond the scope and scale of Carter’s announcement. But he is president for only another nine months, and his successor may have less reticence in these matters. More than that, he has set the logic for his successor to escalate the fight and still think—or at least claim—that he or she is simply continuing Obama’s strategy under changing circumstances. In fact, if the campaign to retake Mosul begins, and the local forces—the Iraqi soldiers, the Kurdish peshmerga, and whatever sectarian militias can be drawn into the fight—are repelled, if they’re facing defeat despite the U.S. artillery and air support, would even Obama let them lose? Or would he give the green light to his generals’ plan (which they would no doubt recommend in this scenario) to let the American soldiers take a direct role in the fight, to drop the fig leaf of “advisers” and don the explicit tag of “combat troops,” which they’re coming close to resembling anyway?