“American leadership”, President Joe Biden declared in the State of the Union address, “means ending the forever war in Afghanistan.” His phrasing itself is significant. It aligns “leadership” with restraint and limitation, rather than expansive foreign policy goals. Biden has shown prudence and fortitude in deciding to withdraw U.S. troops by the autumn. He went against military and civilian advice, and dire warnings from the national security establishment. But in the politics of drawing down from America’s longest war, this is not the end.

The hardest task will not be getting out but staying out

The hardest task will not be getting out but staying out. The gravitational pull drawing the US back into Afghanistan will be strong. It will come from two interacting forces. Deteriorating conditions within the afflicted, conflict-ridden country will create demand to reinsert an American presence. And judging by the denunciations of withdrawal that have already appeared, an enduring worldview within Washington DC will exert pressure from within. By this standpoint, America will have no choice. The assumption is echoed in the words of Former Secretary of State Condoleezza Rice to the House Foreign Affairs Committee: “We’re probably gonna have to go back.”

After America leaves, Afghanistan’s harrowing two decades of war will enter a new phase. Two dismal scenarios are possible. The country could descend into a brutal stalemate, with Kabul a beleaguered island in an ocean of hostile Islamists and warlords, and with regional powers backing proxies. Actors the US fears will be active include Al Qaeda, ISIL and straightforward criminal networks. This will raise fears about a contagion of regional instability, creating nightmares, for instance, over the fate of Pakistan with its nuclear arsenal.

As Afghanistan becomes a battleground for other countries’ rivalries, it will be easy to blame America’s absence, even if those very conditions reveal the failure of protracted, expensive nation-building. With Islamists conducting operations, there will inevitably be arguments made that US standoff strikes are not enough, and that a ground presence is needed to obtain actionable intelligence on terrorism, to coordinate air strikes, to reassure Kabul of American support, and to create leverage to contain the instability.

There is a general disappointment with the wars of our time, especially amongst veterans

Alternatively, if Afghanistan’s army and its backers prove incapable of holding the ring, the Taliban could overrun Kabul and much of the country. The Taliban’s triumph will readily appear to increase the threat of mass-casualty terrorism. Hawks will argue that America’s continent is again dangerously threatened, assuming the world can easily slip back into the conditions that led to the 9/11 attacks. More than any other country in the Middle East, Afghanistan’s linkage to 9/11 gives it a peculiar status in America as a place too wild to try to transform, but too dangerous to ignore.

And convinced world affairs pivot on US decisions even in remote places, these DC voices will blame the withdrawal from Kabul for adverse developments elsewhere, even ones that began beforehand, from Ukraine to Iran to Taiwan. Hawks will make Afghanistan about everything, stressing the need to restore credibility and resolve to allies and adversaries alike. They will paint US adversaries not as real countries pursuing their interests, but reckless predators fixated on testing American will.

Advocates of a return have advantages. This is not the Vietnam war, which for America was a national agony, being vastly more polarising and lethal, and whose pain was spread by the draft. Even while claiming the stakes are high, “returners” can simultaneously argue — and already do — that only a small enabling force of a few thousand personnel is needed, thus is eminently affordable, as well as being absolutely critical.

The financial costs, Returners will argue, will be pennies on the dollar. US casualties, they can claim, will remain tolerably low. Some will present it as a frontier policing mission, barely counting as “war” at all. Even if the Taliban seizes power, a plausible case can be made for an economical intervention. Recall that the American military was able to oust the Taliban in 2001 by aiding local allies with a relatively light combination of special forces, bribes and airstrikes.

The coalition for going back in will mix the hard-headed with the humanist

Indeed, the Afghanistan war has long appeared sustainable because, for most Americans, it and the wider War on Terror is a remote undertaking far from their lives. The state insulates the populace from it, deploying professional soldiers and private contractors rather than shouldering the burden with citizen-soldiers (“voters”) or conscription. And funds it not through taxation but through borrowing, urging voters to go shopping rather than engage. Hence the lack of direct backlash.

The main impetus for a return will come from Washington. A well-placed coalition, cohesive and influential in government and think-tanks, with strong media access, will portray abandonment as both an unacceptable blow to national security and a moral failure. Resurgent chaos in Afghanistan will revive the enduring, bipartisan belief that the wider region still matters enough for the US to stand sentry, albeit in a more limited posture.

The coalition for going back in will mix the hard-headed with the humanist. While a war to emancipate Afghan women and protect humanitarian gains may have lost appeal for the moment, this could quickly change. A missionary impulse in US foreign policy will return, one that can sooth progressive-minded doubters. No responsible global leader can abide beheadings or gender apartheid, we will hear, let alone terrorist sanctuaries. America must act.

And then there is public opinion. Mass sentiment about foreign policy is volatile. True, there is a general disappointment with the wars of our time, especially amongst veterans, and solid majorities of the public presently support drawing down. But the eruption of post-withdrawal chaos, graphic images of Islamist atrocities, and above all the renewed fear of terrorism, could well see a tilt in opinion back towards projecting power, especially if most Americans are spared taxation or bereavement as a result. Support for staying out may prove broad, but shallow.

After all, the rise of ISIL in 2014 precipitated a return of US forces to Iraq, the scene of a war much more bitterly resented domestically, as well as Syria. Significantly, America went back in under a reluctant president who favoured a rebalancing “pivot” towards Asia. This return attracted majority popular support. It resulted in garrisons and bombing campaigns and extensive diplomatic engagement, and extended to longer-term commitments. There was, note well, fierce bureaucratic resistance to withdrawal. Around these literal and intellectual boots on the ground, further rationales for staying accumulated — from countering Iran to checking Russia to ensuring ISIL’s “enduring defeat”.

The same could happen again. Recreating a small garrison in Afghanistan will provide a platform for a larger presence. If the US stays and the Taliban mounts a large-scale offensive to evict the US, as is likely, and inflicts American casualties, this will create pressure for reinforcement. What withdrawal led to “last time” will haunt the debate. Once again, given fears of further consequences and the difficulty of claiming victory, such a commitment will be hard to wind down.

It is not enough to draw down forces or de-prioritise theatres of war and hope those neighbourhoods stay quiet

The arguments for leaving and staying out are strong. Some will argue that an Islamist foothold in Afghanistan is intolerably dangerous, that a military presence is necessary to deny it, and that it took a two-decade mission to prevent large-scale terrorist attacks on American soil. Yet no country in the region, with ground troops or without, has produced such an attack. This suggests such attacks can be disrupted with other measures. Afghanistan was never an especially valuable platform for projecting power. Even the 9/11 attacks depended on forward operating positions — meeting places in Hamburg, flight schools in Florida — that are now under close scrutiny.

As for claims that withdrawal “there” means erosion of America’s stocks everywhere: fighting protracted peripheral wars tends to generate a reputation for fighting protracted peripheral wars. It is more likely to excite pity — or counter-balancing — than stiffen allies’ confidence. Historically such embroilments — be they in Algeria, Vietnam, Lebanon or Afghanistan — have made the occupiers appear more depleted than resolute. And retreats from draining commitments can be the basis for strategic renewal.

But the merit of staying or leaving is beside the point. If after America departs, the country fractures into a long-term civil war, or if the Taliban march on Kabul, the case for action on the ground will be intuitively appealing to many.

Demand for going back into Afghanistan will be rooted most deeply in a set of beliefs about the world. One belief in particular remains intact, even in an age of renewed great power competition concentrated mostly in East Asia. Namely, the fear of dominoes falling globally, both physical and psychological. In this world view, remaining present is necessary, both to deter adversaries and to bolster America’s reputation as a global alliance guarantor. Retreat somewhere, some fear, will weaken the whole ecosystem, as the world is a fragile interconnected place.

To avoid long, grinding struggles in the Greater Middle East, it is not enough to draw down forces or de-prioritise theatres of war and hope those neighbourhoods stay quiet. American leaders should recognise that violent disorder is likely to flow from resulting power vacuums in a region declining in salience, but that the US can and must live with it, managing the fallout from a distance. In the absence of such a reassessment of American interests, so long as the fear of falling dominoes endures, and the US retains its reach, there is a serious chance of a return. “Do something” is a dangerous and presumptuous reaction to events. It’s a luxury of the powerful, but indulging it does nothing to conserve that power.