NEW YORK — French President Francois Hollande pledged a "pitiless" war on ISIS after Friday's Paris massacre. Russian President Vladimir Putin says his nation is focused on "finding and punishing the perpetrators" who downed a Russian passenger jet over Egypt. U.S. President Barack Obama says the goal is to "degrade and ultimately destroy this barbaric terrorist organization."

How? That's the question none of these men seems willing to answer. Here's one idea that, while not optimal militarily, might hedge the political risk: Form a broad alliance, akin to the one that pushed Saddam Hussein's forces out of Kuwait in 1991, to coordinate a ground attack on the jihadist army.

Nobody thinks it would be easy. The idea of Western troops working with Russian ones so soon after Putin's aggression in Ukraine is implausible and distasteful. But as long as these leaders rule out boots on the ground, either solo or as a group effort, their strong words are at best contradictory and at worst hypocritical.

There have been signs of cooperation. French jets, guided by American intelligence, have carried out bombing raids of the jihadists' de facto capital in Syria, Raqqa. Putin has told his navy to cooperate with French warships in the Mediterranean. The U.S. and Russia worked out a way to avoid shooting each other's planes.

Hot air

But mostly, there's more talk than consequential action. British Prime Minister David Cameron vowed to "wipe out" ISIS, but called only for increasing the Royal Air Force's participation in airstrikes. King Abdullah of Jordan, which is a member of the American-led coalition giving air support to Kurdish and Syrian rebel fighters, said after the Paris attacks that Muslims should take "collective responsibility" for defeating ISIS. But he offered no plan to create a meaningful coalition with the Gulf states or Egypt.

Troops are required

No informed military analyst thinks bombs alone can do the job. Many experts, even some of Obama's advisers, are almost as skeptical of the notion that airstrikes could enable a victory by local forces in the region.

Peter Mansoor, a retired Army colonel who was executive officer to Gen. David Petraeus during the Iraq surge: "Drones and air strikes are tools of war, but they are not a strategy. The destruction of the Islamic State requires capable ground forces."

David E. Johnson, a retired Army colonel and analyst at the RAND Corporation: "Competent ground forces are fundamental to the joint force equation for finding and defeating adversaries. Attempting to impart this competence to another ground force is folly."

James Jeffrey, U.S. ambassador to Iraq from 2010 to 2012: "The president says his goal is to "degrade and destroy" ISIS, but you're not going to do that with some additional airstrikes."

Buck Sexton, a former CIA counterterrorism analyst: "If ISIS is to be defeated, the path forward must be elite U.S. troops."

What about those ground troops already in the fight? The Kurdish peshmerga and Western-backed Syrian anti-government rebels took the Iraqi city of Sinjar from ISIS troops last week. There's also the Iraqi army and Iranian-backed Shiite militias. A strategy of backing indigenous forces has worked before: Think of the Northern Alliance's rapid removal of the Taliban in Afghanistan in 2001.

But a closer look reveals that this is a poor precedent. The Northern Alliance consisted of experienced forces that had played a critical role in defeating the Soviet Union. While the U.S. footprint was light initially, there was a willingness to risk American lives, as 1,000 Marines took part in the liberation of Kandahar alone.

Even so, success was fleeting. The Taliban fell back to the south of the country and eventually over the border into Pakistan. This incomplete victory eventually led to 100,000 U.S. troops in the country a decade later, with nearly 2,400 killed. Now the Taliban is getting stronger. (Why wouldn't ISIS follow the same melt-away-and-wait strategy? A big reason is that its apocalyptic narrative holds that the day of judgment will center around the town of Dabiq in Iraq, which therefore cannot fall into the hands of the infidel.)

Local forces not enough

Other recent attempts to boost local forces with air power have had even less success. Consider the current fiasco in Yemen, or the condition of Libya.

Efforts to create a friendly force of Syrian rebels have foundered. A $500 million initiative was abandoned last month after it produced only a handful of trainees.

The Iraqi army has been a punch line since forces dropped their weapons fleeing ISIS in Mosul last year. Shia militias have performed better, but Baghdad's primary goal is likely to be retaking its territory and pushing ISIS back into Syria, not obliterating it.

As well as the Kurds have performed recently, they too seem unlikely to pursue ISIS to the last man. Syria's Bashar al-Assad has consistently ducked the fight against the jihadists, focusing his attacks on the Western-backed rebels and civilian areas.

So if eliminating ISIS is the goal, why won't world leaders commit to sending their own troops? Obama has plenty of reasons: Americans are likely to have a limited tolerance for casualties after 14 years of war in Afghanistan and Iraq. He has consistently pledged to end those bloody entanglements.

Putin, the virtual tsar, would seem to have fewer political worries, but Russia had its own Afghan debacle. Cameron isn't even certain that his plan to increase air support will make it through parliament. Hollande, while urging a global "unity of strength" and pushing for United Nations Security Council action, hasn't broached the idea of French boots on the ground.

The only nation that seems willing to put its troops in harm's way is Turkey. Still, Prime Minister Ahmet Davutoglu made it understandably clear last week that his nation would not act unilaterally.

There have been hints of action from Arab states, but nothing more. Jordan has a competent military of 100,000, including 12,000 special-operations troops. It remains on its own side of the border with Iraq and Syria.

So the question is: With nobody willing to go it alone, could the military load be shared? The Gulf War coalition had its odd bedfellows, including Syria, then under the control of Bashar al-Assad's father, Hafez. And while the U.S. and Iran are not technically cooperating in Iraq, they discussed it during nuclear negotiations in Vienna last year, and their training operations for the Iraqi army have edged closer together.

Tactically speaking, a broad coalition would create problems. Many experts feel the NATO-izing of the Afghan war made the chain of command more cumbersome. The Gulf war was always in essence a U.S. operation — the biggest contribution of the Arab states was financial, not military. In terms of speed and efficiency, the U.S. would certainly be better off sending ground troops against ISIS on its own, albeit coordinated with Russia"s military to avoid an accidental conflict.

But as long as Obama and fellow world leaders feel they need to play it safe, sharing the burden might be the only way to hit ISIS with all that's needed.