ONCE again, and more wearily than ever, America is saddling up to lead an armed posse into the badlands of Mesopotamia. In 1991 the elder George Bush gathered a coalition to chase the invading forces of Saddam Hussein’s Iraq from Kuwait. In 2003, ostensibly but misguidedly as part of his global war on terror, the younger Mr Bush invaded Iraq, rid the country of Saddam but then got bloodily stuck; it took a vast commitment of American troops and fresh thinking to bring the violence under control. Now Barack Obama, having extricated American forces in 2011, has announced a new campaign to “degrade and ultimately destroy” the jihadists who burst out of Syria and reached the gates of Baghdad.

Today’s foes are an especially vile cast of Sunni zealots, killers and misfits calling themselves Islamic State (IS). An offshoot of al-Qaeda, IS has exceeded its progenitor in terms of both political ambition and brutality. Across swathes of Syria and Iraq it has founded a “caliphate”, the long-defunct Islamic institution that the late leader of al-Qaeda, Osama bin Laden, only dreamed about in messianic discourses.

IS’s love of gore, with gleeful massacres and beheadings recorded for video distribution across the internet, the brutal persecution of religious minorities and, it is said, the enslavement of women and children, has estranged it even from al-Qaeda. IS is a “killing and destruction machine”, says Abu Qatada, a jihadist ideologue (once described as Bin Laden’s top man in Europe) who was extradited from Britain to Jordan, where he is on trial on terrorism-related charges; its fighters are the “dogs of hellfire”. The beheading of two American journalists gave the West a glimpse of the many horrors.

IS has achieved something scarcely conceivable in the Middle East by uniting the bitterest of foes in a common purpose. Such diverse actors as Europeans and Kurds, the embattled Syrian regime along with many of the rebels opposing it, Turkey, a slew of Arab states, as well as Israel and the Iraqi government itself have all clamoured for American intervention. Even Iran, though unenthusiastic about the Americans’ return to a theatre that it has worked hard to squeeze them out of, has accepted a tacit, temporary alliance with the Great Satan.

On September 10th, Barack Obama promised to “lead a broad coalition to roll back this terrorist threat”. This would include systematic air strikes against IS in support of Iraqi forces and, if necessary, in Syria too.

Turning the fleeting political alignment into a coherent campaign is a tall order. The invasions of Afghanistan and Iraq have shown how Western armed forces can score quick initial victories, but fail to secure a stable political system to maintain security thereafter. It may be even harder given that Mr Obama, even as he deploys hundreds more soldiers to support the mission, insists America “will not get dragged into another ground war”.

From Baath to bloodbath

The strength of IS reflects the political implosion in much of the Middle East, from the destruction of Saddam Hussein’s Baathist dictatorship by the Americans to the cracking of Bashar al-Assad’s Syrian one in the succession of Arab uprisings known as the Arab Spring. IS is both the product and the chief instigator of the ever deepening Sunni-Shia enmity that runs from Bahrain to Lebanon.

Misrule and cynicism play a part, too. IS could not have established itself in Raqqa, in Syria’s north-east, had Mr Assad not held off from bombing it, though he had no qualms about killing civilians elsewhere in his attempt to crush less extreme opponents; Mr Assad’s aim was to present himself as the only alternative to the most terrifying of jihadists. And IS could not have taken control of swathes of Iraq this summer, including Mosul, the second-largest city, had it not been for the systematic marginalisation of Sunnis by the Shia-led government of Nuri al-Maliki.

IS has become bigger, better armed and financed and more brutal than other terrorist outfits. It is reckoned to earn some $1m per day from selling oil and ransoming hostages. According to recent intelligence estimates, IS and its allies count up to 30,000-45,000 men, roughly a third of whom are thought to be highly skilled fighters. It has mobilised foreign recruits faster than groups in other conflicts, partly because of the ease of access to Syria through Turkey. Estimates for foreign passport-holders vary, but there may be 12,000 operating in Syria (perhaps 3,000 of them Westerners) of which the majority have gravitated towards IS because it offers more glamour, money and, recently, success than other rival groups, such as the official al-Qaeda affiliate, Jabhat al-Nusra.

IS grew out of the remnants of al-Qaeda in Iraq (AQI), which was temporarily crushed by the American-instigated awakening, or “Sahwa”, of Sunni tribes in Anbar province in 2007-08. It has fomented sectarian division by carrying out suicide bombings against Shias in Baghdad. It has also attacked prisons, for instance in July 2013, when an assault on the notorious Abu Ghraib and another jail freed some 500 AQI veterans, including many former commanders.

A lot of its success stems from the team that the group’s leader, Abu Bakr al-Baghdadi, has gathered. Quite a few are former senior officers from Saddam’s army who took to violent resistance after being banned from re-enlisting under the de-Baathification policies of America and successive Iraqi governments.

Land of two wars

IS’s war has washed from one side of Iraq’s border with Syria to the other. As it set up its base in Raqqa, it showed a greater appetite for fighting other rebel groups than the Assad regime. With the seizure of Mosul on June 10th, where the Iraqi army was routed, IS acquired a huge stockpile of American-supplied weapons: armoured vehicles, artillery, anti-tank and anti-aircraft missiles, fleets of Humvees and a vast quantity of ammunition. Thus strengthened, it cleared out the last Syrian forces from Raqqa province. Three weeks ago it took the al-Tabqa airfield in possibly the most significant and bloody defeat suffered by the regime since the start of the uprising three years ago.

What has characterised IS so far is its combination of strategic patience, the ability to design and direct complex military operations simultaneously in Syria and Iraq, and hybrid warfare that fuses terrorist and insurgent techniques with conventional fighting. Among the tactics it has developed is to soften targets with artillery, or open a breach with suicide bombings, and then attack with swarms of armoured Humvees mounted with anti-aircraft guns coming from what seems like all directions at once. Its aggression, speed, firepower and readiness to take casualties, combined with the well-publicised savagery that awaits anyone taken captive, terrorises defenders into flight.

While al-Qaeda lurked in the shadows and sought to attack America and Europe, which it called the “far enemy”, intelligence agencies think that, for the time being, IS’s preoccupation is the “near enemy”. That offers scant comfort, as IS threatens to destabilise a large part of the volatile Middle East. Success may inspire others: Boko Haram in Nigeria has begun to emulate IS’s tactic of seizing and trying to hold territory.

With its ideological ferocity, attachment to the “propaganda of the deed”, organisational skill, platoons of Western passport-holders, hatred of America and determination to become the leader of global jihadism, IS will surely turn, sooner or later, against the far enemy. The ability of IS to act as a magnet for foreigners, particularly radicalised young Muslims from Europe, is deepening Western fears that some hardened fighters will want to return home to plot self-directed attacks. The danger of such “lone wolves” was apparent in the killing of four people at the Jewish museum in Brussels in May. The presumed attacker, Mehdi Nemmouche, a Frenchman of Algerian descent, has been identified by French former hostages in Syria as one of their jailers.

Few analysts think the beheading of American journalists, which spurred Mr Obama to announce his strategy, was really an attempt to goad the West into returning to the region. It was, perhaps, retaliation for initial American air strikes, and a warning to desist. Or perhaps it was just a “a declaration of impunity”, says Jessica Lewis, a former American intelligence officer in Iraq who works at the Institute for the Study of War in Washington, DC.

IS members who appear on social media view the prospect of more intense American action with a mixture of glee and fear. For all its successes, IS also has big weaknesses. The alliance of hard-core jihadists and former Baathists could fracture under pressure. And IS is paranoid about local populations turning against it, which helps explain its brutal expulsion of minorities and moderate Sunnis from areas it controls. By choosing to create a “state” the organisation must now defend a territory stretching some 460 miles (740km) from Baghdad to Aleppo. And when IS forces go on the offensive they must drive along open roads through mainly flat terrain that offers little cover from aerial attacks.

The limited air strikes that America has conducted so far (about 150 to date) have brought humanitarian relief to the Yazidi minority, allowed outgunned Kurdish Peshmerga fighters to repel an IS advance near Kirkuk and, working with Iraqi security forces, preserved the Mosul and Haditha dams in government hands. With American support, Iraqi troops and Shia militias lifted the siege of the town of Amerli, home to Shia Turkmen. A larger air campaign could destroy many of the armoured vehicles and heavy weapons that have provided IS with the mobility and firepower to rampage across Iraq.

Ground-to-air support

Although air power may contain IS, it will take ground forces to push its fighters out of the Sunni cities it has taken—and keep them out. But whose troops? The Peshmerga enjoy a reputation for being fearless fighters, but they needed American air strikes to prevent their regional capital, Erbil, from falling. The Kurds are now being hurriedly armed by Western countries, but they are unlikely to advance far beyond their semi-independent enclave. Shia militias are hardly more savoury than IS itself. Even Muqtada al-Sadr, a radical Shia cleric, this week had to disavow atrocities carried out by Shia fighters ostensibly loyal to him; they were said to have killed and beheaded several Sunnis and burned homes in the fighting for Amerli.

On the march, perhaps not for long Expelling IS will need, above all, the co-operation of Iraq’s disgruntled Sunni tribes, for whom the group is either a protector or at least a convenient ally against the Shia-led government and myriad Shia militias. Pushed by both America and Iran, the divisive and discredited Mr Maliki has been replaced by Haider al-Abadi, who this week won parliamentary support for a new government. But it will take much more than fresh faces to dispel Sunni suspicions. After all, Mr Maliki appointed Sunni ministers, and Mr Abadi hails from the same Dawa party. “We will keep fighting alongside IS since we lost so many people under Maliki,” says Tahsein, a fighter from Karma in Iraq’s Anbar province. It will be hard to recreate the Sahwa. For a start, there is no large American presence on the ground (there may be some special forces) that can offer protection, be it from Sunni or Shia killers. In any case Mr Abadi is thinking of a different model, with a new government-financed and supervised paramilitary force in each province. Whether such outfits will prove any more effective than the hapless Iraqi army is open to doubt. Michael O’Hanlon of the Brookings Institution, an American think-tank, argues that American “security-force assistance teams”, each with about 10-20 soldiers, need to be deployed with Iraqi battalions for a year or so. Several thousand special forces working with the Iraqis may be needed to carry out sufficient “kill or capture” raids to remove the most dedicated IS fighters from the battlefield.

What to do about Assad

Fighting insurgents is infinitely harder when they enjoy a haven. Any strategy against IS must, sooner or later, involve reducing the group’s heartland in eastern Syria. But here Mr Obama’s plan is weakest. In Iraq he has outlined a counter-insurgency campaign combining Iraqi ground forces and American air power. In Syria he is talking mainly of a counter-terrorist operation, involving air strikes of the sort America carries out in Yemen and Somalia against high-profile targets—such as the one that killed the leader of Somalia’s Shabab militia earlier this month (see article).

To an extent, the two-prongpolicy reflects reality. In Iraq there is a government of sorts that, for all its flaws, can ask for external support and might be cajoled into reforms. In Syria the regime of Mr Assad is as loathsome as IS, and indeed acquiesced in its expansion. America knows, moreover, that Russia may well block any UN authorisation for military action in Syria, as it has done in the past. That said, Mr Obama’s commitment to strengthen the non-IS opposition is vague and has come very late in the day. Less extreme Sunni rebels pushed out IS in the north-western provinces of Idleb and Aleppo early this year, but have since fallen back and are now caught in a pincer between IS and pro-Assad forces. Mr Obama gave no hint of how he intends to pursue the “political solution” to end Syria’s civil war, which has uprooted nearly half its 23m people and, by one estimate, killed at least 110,000 civilians (see chart).

To some, co-operation with Syria may be the lesser evil, if only to ensure that Syrian missiles do not shoot down coalition aircraft. But Syria’s air defences are not an insurmountable threat to Western aircraft. Syria’s army, moreover, is thinly spread, tired and demoralised. Mr Assad, whose Alawite sect is an esoteric offshoot of Shiism, has relied heavily on Shia fighters brought in from Iraq and Lebanon. Helping Mr Assad, directly or indirectly, would risk casting America as the agent of Iran and the Shias.

All these difficulties point to the need for broad support. The more allies America can gather—particularly Arab and Sunni ones—the more legitimate the war against IS will seem in the eyes of Sunnis and of the rest of the world. It helps that Saudi Arabia is willing to do more to train and equip Syrian fighters. Others have yet to say what they are prepared to do.

The diplomatic game is particularly hard. America is losing its hegemony in the Middle East, while the region itself has grown radically more fragmented and volatile. On top of such unresolved conflicts as the one between Israel and the Arabs, or between Turkey and Kurdish insurrectionists, the schism between Sunni and Shia has been exacerbated by a shadowy proxy struggle between the two sects’ main state champions, Iran and Saudi Arabia.

Elsewhere in the region the turbulence of the Arab spring has left surviving regimes, or resurrected ones such as Egypt’s military-dominated government, far more wary and mistrustful of their traditional Western allies than ever. Conservative Arab rulers suspect America of having plotted to undermine them, and of foolishly seeking a nuclear deal with Iran as a silver bullet for regional woes. In addition, countries such as Turkey and Qatar, which backed the losing horse of Egypt’s Muslim Brotherhood, are no longer seen as reliable partners by other Arabs.

The long war

Given the complex of military and political problems, Mr Obama is right not to put a time limit on the mission, as he has done too often in the past. The military tide may already be turning. In Iraq IS is losing some of the capacity to surprise, and has run to the limit of its ethnic base. Without the magical aura of momentum, there is at least a possibility that IS could wane almost as quickly as it waxed.

And yet, from the moment IS is seen to falter, and even before, the strange bedfellows now united against the group are nearly certain to fall out among themselves. Trying to stop them doing so, or at least to lessen the damage from inevitable frictions, will take a broader approach. Mr Obama may succeed in clobbering IS. But the jihadists are a gruesome manifestation of a wider problem that Mr Obama seems unwilling to tackle: how to fashion a future for Iraq and Syria that is attractive enough to secure consent from majorities of their citizens, Sunnis, Shias, Kurds and everyone else.