If dollars spent and airstrikes unleashed were guarantors of victory, the United States, France and their allies would have already dispatched to history the jihadist militants known as the Islamic State group, aka ISIS. Since August 2014, the Obama administration has devoted more than $5 billion --  roughly $11 million per day -- toward Operation Inherent Resolve, the mission launched to “degrade and defeat” ISIS in Iraq and Syria. By early last month, the airstrikes had damaged or destroyed nearly 14,000 ISIS targets, by American accounting.

Yet anyone under the impression that ISIS was teetering toward irrelevance got a disturbing jolt of reality Friday as the militants deployed apparent sleeper cells -- covert units hiding in wait -- to administer a coordinated and devastating series of assaults in Paris, leaving 129 people dead and about 350 injured. “This attack is the first of the storm,” the extremist group said in a statement posted Saturday, claiming responsibility for the carnage.  

Within hours of those attacks, both the French and American presidents had issued fresh vows of military vengeance. “We are going to lead a war which will be pitiless,” French President Francois Hollande said, following through on that declaration Sunday, with airstrikes hitting ISIS targets in the group’s de facto capital of Raqqa, Syria.

But an intensified military campaign against ISIS is by itself unlikely to defeat the militants in the Middle East or beyond, experts told International Business Times. Effectively pacifying the organization will require more than launching airstrikes while arming and training opposition groups; it will depend upon fostering a process of political reconciliation that alleviates the grievances of local populations. It will also require the development of local institutions to ensure that communities feel safe and that families are able to put food on the table. From Afghanistan to Iraq, recent history has shown that, absent these complementary efforts, attempts to bomb extremist insurgents into permanent oblivion tend to fail, experts said.

“This is a complex battle. It requires two parallel tracks: the ideological-political track and the military track,” said Fawaz Gerges, a professor at the London School of Economics and an expert on ISIS and Al Qaeda. “You can’t just press a button to resolve it.”

ISIS emerged in June 2014 when it seized control of large swaths of Iraq. By the end of that month, it had declared a caliphate in parts of Iraq and neighboring Syria. Since then, it has killed thousands of civilians, sold women into sex slavery, massacred religious and ethnic minorities and brutally executed people after taking them hostage.

For more than a year, a U.S.-led coalition has launched airstrikes against the group. U.S. Deputy National Security Advisor Ben Rhodes said Sunday that the U.S. would share military intelligence with France and intensify airstrikes against the group in Iraq and Syria. But a program to vet, train and arm Syrian rebel groups was suspended in early October after more than half the recruits were expelled or quit. Since then, ISIS has lost ground militarily in Iraq but succeeded in carrying out a series of brutal terror attacks in Paris and twin suicide bombings in Beirut.

Experts in the workings of jihadist groups assert that a military element is necessary to combat ISIS, but many say the current strategy in place is both shortsighted and simplistic, lacking the well-roundedness to ensure that military gains can be built upon.

“Airpower has helped limit the group’s advances, but to push it back further, more effective ground power is necessary,” Daniel Byman, research director at the Center for Middle East Policy at the Brookings Institute, a research group in Washington, said in an email Sunday.

At the same time, a single-pronged strategy of trying to cut down ISIS militarily risks leaving a power vacuum in its wake -- the very environment that is conducive to extremist groups' growth. The U.S. and its allies want to destroy ISIS, but who, or what, would take its place remains a pressing question and a formidable challenge.

“Western countries’ unwillingness to deploy large numbers of combat troops and the weaknesses of local allies have made this a persistent problem,” Byman said. Meanwhile, infighting among groups on the ground as well as rampant corruption have made it difficult to ensure that gains against ISIS aren’t wasted. “Many [local groups] don’t fight particularly well,” he added.

Some maintain that getting local support is the only way to go -- despite the challenges in strengthening local forces so that they become more effective -- since they are crucial in shoring up whatever gains are made against ISIS.

“ISIS needs to be defeated militarily because it’s an expansionist terrorist organization that wants to fill vacuums wherever it finds them in the Middle East,” Alex Vatanka, an expert at the Middle East Institute in Washington, said. “But what’s important is that it is just not a military campaign where you defeat it and forget about it and walk away.”

A Black Market Crackdown

Before the U.S. began airstrikes against the Islamic State group, a U.S. official estimated that it raked in $2 million per day in oil profits, selling to groups in Syria and Iraq, as well as to the Syrian regime. That estimate has since dropped to $8 million to $10 million per month, but the implications remain clear: ISIS has funding to fuel its fighting.

But if penalties were imposed on those who bought oil from the group, that could weaken it, Vatanka said. France could play a key role in pressuring countries in the Middle East, particularly those in the Persian Gulf region, to stop the flow of arms and money to ISIS -- something the United States and other countries have failed to do.

“The French are well-equipped to take the lead here,” Vatanka said. Not only does it have a long history, albeit a fraught one, in the Middle East, but it has the incentive to do so as it reels from the worst attacks on its soil since World War II. It could pressure countries in the region to crack down on the black market for oil, he suggested.

Others said France will not necessarily have to take the lead in the economic battle against ISIS. Even though the group's sources of revenue are primarily in the black market -- it also sells stolen and looted antiquities, for instance -- economic sanctions like the ones that forced Iran to the negotiating table this year, could work, David Schanzer, director of the Triangle Center on Terrorism and Homeland Security at Duke University, told IBT. “We need everyone’s cooperation -- Russia, Turkey, all the surrounding countries -- to try to shut off these black market forms of finance that ISIS is able to use to raise revenue,” he said.

Nor would an economic crackdown on ISIS' sources of revenue necessarily have to come down directly on the militant group itself. Instead, countries trying to combat the group could use their own economic strength to enlist the help of regional leaders, such as Saudi Arabia, and demand that they step up in combating extremism.

Countries could threaten to buy less oil or reduce their trade with those countries, Vatanka suggested. “Once you start squeezing them, I think they‘ll be much more inclined to help in a more meaningful way than they have been,” he said.

‘A Battle Of Decades’

But perhaps the most slippery front in the war against ISIS is the ideological one, which is not just about the eradication of the ideas that draw the extremist group’s supporters but also about convincing those involved in the Middle East quagmire that tackling the organization is a priority.

“Common U.S., U.K. policy is to target leaders and high-level members of radical groups,” said Emma El Badawy, a senior analyst at the Center on Religion and Geopolitics at the University of Exeter. But that strategy has a key flaw. “Killing Osama Bin Laden, for example, did nothing to destroy al Qaeda,” she pointed out. “After killing a leader, there are so many more willing to take his place -- some with even more extreme views.”

ISIS in its current form is little more than a year old, but the extreme Islamist ideology at its heart is far older. Effective methods of countering this ideology are lacking.

“This is a battle of decades. This is not an ideology that was born yesterday,” Schanzer said. “We are really at an early stage of learning to understand how best to turn the tide and discredit these ideas.”

The idea that by joining ISIS, people can be special, or contribute to something greater than themselves, is immensely powerful. So is the the religious element that justifies the group’s criminal actions by calling it God’s work, said Justin Crump, a security and intelligence expert, who is CEO of U.K.-based security consulting firm Sibylline. “One of the things you struggle with is Western countries not being able to understand the importance of religion in this,” he said. “It’s beguiling,” he added, explaining that ISIS essentially tells recruits, “We can give you certainty in your life, and it’s fine to be violent.”

Not everyone is convinced that the ideological battle can be won.

“It is far harder, and historically less effective, to try to win over the hearts and minds of would-be jihadists,” Byman, the expert from Brookings, said.

The ideological battle also doesn’t revolve solely around turning would-be jihadists away from the cause; it’s about first convincing key players involved in the civil war in Syria that ISIS is a critical adversary. For Russia, defeating the Islamic State group comes second to bolstering the regime of embattled  Syrian President Bashar Assad.

“If everyone agrees that Assad is the lesser evil of the two, then you can really do plenty in terms of putting the pressure on ISIS,” Vatanka said. “You’ve got to come down to the most basic message: It’s ISIS against everybody else.”

Political and ideological unity is essential to defeating ISIS, experts said, but the path to arrive there is unmarked. For the lure of the extremist group to be diminished, it has to be replaced with something better to ensure it doesn’t re-emerge in yet another incarnation. Yet, as in the cases of Iraq and Afghanistan, the United States in particular has struggled with such a daunting task, which cannot fall to one country alone, experts said.

“The problem we have to focus on now is making sure that the entire villages and towns that in 2014 embraced ISIS doesn’t happen again,” Vatanka said. “You’ve got to give them alternative -- something to look forward to the day after ISIS,” he said. Vatanka added that that would take a political process of reconciliation and redistributing power so that those who have felt marginalized -- like Sunnis in Syria and Iraq -- do not see extremist groups as a better alternative.

It’s a lesson the U.S. and its allies learned from their time in Iraq, after the 2003 invasion.

“ISIS is a product of the failed political process in the past, when we defeated the Islamic State in Iraq,” Vatanka said. “Then they re-emerged, just under a new name and more vicious than before.”