The Paris attacks and the downing of a Russian airliner have heightened determination in Moscow, Paris and Washington to defeat Islamic State, a challenge easier said than done.  Many strategists say military advances will show little progress unless more work is done to eliminate the militant group’s financing, counter its propaganda and cut a diplomatic deal among world powers on Syrian rule.  For military planners, destroying the terrorist group’s headquarters and crippling its fighting force is a relatively simple assignment, say strategists: It would require some 40,000 troops, air support and two months of fighting.  The problem is what do to after taking responsibility for won territory. With the recent experience of Afghanistan and Iraq, that is a job no Western leader wants. Many officials, especially in Europe, believe a full-scale military response would help Islamic State, also known as ISIS and ISIL, by broadcasting an image of Westerners seizing Arab lands, attracting more followers to the militants’ cause.  “Drawing us into a ground war with them is a trap,” said a French government official. “Frankly, I doubt it would go very well.”  The options short of a ground invasion are limited. After fighting Islamic State for more than a year through airstrikes in Iraq and Syria, military officers, diplomats and analysts agree there is no easy formula for victory.  Western allies are developing ways to escalate their operations and shift tactics. France is stepping up air attacks and bringing in 24 planes on the aircraft carrier Charles de Gaulle, which will arrive in the eastern Mediterranean next week to triple French air power in the region.  The U.S. military has developed options to accelerate the fight against Islamic State, including measures designed to strengthen local partners—Kurdish forces, for example, in Iraq and Syria—against the militants.  The U.S. also is considering creation of a base in Iraq to launch raids on Islamic State leaders; tripling the number of special operation forces working in Syria; and expanding the list of Islamic State targets by risking additional civilian casualties in more aggressive airstrikes.  Derek Chollet, a former Pentagon official with the German Marshall Fund of the U.S. think tank, said taking more aggressive steps, such as sending U.S. forces to the front lines to call in airstrikes, could help in the fight but will take time. Entering into a ground war, he said, could be a mistake.  “We made a lot of decisions as a country in the wake of 9/11, in the fever of fear and the desire to do something decisive, that we are still digging ourselves out of,” he said.  Some strategists say Islamic State may be more vulnerable than it appears. The group seems to have challenged the world, said Michael Clarke, director of the Royal United Services Institute, a defense think tank in London. Islamic State has picked fights not only in the Middle East, but with the U.S., Russia and France. This week it baited Beijing by killing a Chinese hostage.  “They think this is their time in history, their victory is divinely assured,” Mr. Clarke said. “From a strategic point of view, they are making every mistake.”  The Paris attacks—along with the bombing of a Russian plane and attacks in Turkey—have raised the prospect of an alliance between Moscow and the West.  Whether the gestures of solidarity over the past week will continue is an open question. Russian aggression in Ukraine looms in the background. Many Western officials say Europe and the U.S. can’t ignore the annexation of Crimea or Moscow’s support for Ukraine separatists.  And, on Syria, the diplomatic rift remains between Russia, which sees the government of President Bashar al-Assad as the best bulwark against chaos in the region, and the West, which believes the Assad regime is to blame.  “There is the potential for this to work,” said a senior official in the North Atlantic Treaty Organization. “But you have to start any talk about any sort of coalition with a common objective, and we don’t yet have a common objective.”  European diplomats and scholars say both sides may now be willing to compromise. “This string of attacks have had a catalytic effect,” said Marc Pierini, a former European Union diplomat and scholar at the think tank Carnegie Europe. “Something is happening that is entirely new.”  Ian Kearns, the director of the European Leadership Network think tank, said Europe must provide stepped up military support for the moderate opposition fighting the Assad regime in Syria, to both slow the flow of refugees to Europe and to increase bargaining power with Russia.  “The Europeans have to wake up and align their interest and values,” he said.  Much of Islamic State’s strength comes from controlling vast areas of territory in Syria and Iraq, enabling a flow of taxes, oil profits and extortion money. Unlike al Qaeda, which needed foreign financing, Islamic State is largely self-sufficient.  The group doesn’t depend on the global financial system, so cutting off its money supply is difficult. Access to cash allows Islamic State to pay its fighters and bureaucrats, run municipal services, bribe tribes into cooperation and fund its global propaganda operation.  Syrian oil fields are one of its largest revenue sources. Last year, the U.S. Treasury Department estimated Islamic State earned as much as $1 million a day selling oil, which is smuggled to Turkey’s black market or sold locally to domestic refineries.  Since the beginning of its air campaign in Syria, the U.S. has struck Islamic State oil production facilities, which militants have largely been able to repair.  The Pentagon, defense officials said, has by design struck oil facilities to damage, not destroy them. The U.S. had hoped to expel Islamic State without laying waste to the economic infrastructure of Syria and Iraq. The loss of refineries and wells would make economic recovery difficult, military officials said.  Officials are now weighing more damaging attacks. The Pentagon announced this week the bombing of 116 tanker trucks near the eastern Syrian city of Deir Ezzour. French officials said they hoped the oil production facilities hit in their airstrikes this week won’t be so easily repaired.  The job of stopping the flow of oil revenues, officials said, is exceeded only by the task of heading off militants bound for Europe, which requires tightening borders. On Friday, the European Union ordered stricter border controls on its perimeter, a move intended to broaden the systematic police checks of EU citizens and improve the ability of authorities to track potential terror suspects.  The West also faces polished recruitment efforts by Islamic State propaganda machine, officials said. Islamic State operatives have made a big push via social media to project a positive vision of life in its so-called caliphate—both to residents of territory it controls, as well as to Muslims abroad.  U.S. and European officials say the West hasn’t been effective in countering Islamic State propaganda because, in part, it lacks the credibility and immediacy of messages relayed by friends and relatives connected to Islamic State. One way might be to have defectors tell their stories, scholars say.  “I think we are really struggling countering the narrative,” said Colin Clarke, a Rand Corp. political scientist who studies terrorist groups. “I don’t know if we thought long and hard about it, or devoted enough resources.”  Some commentators have raised the prospect of using cyberattacks to cut off Islamic State from the Internet, disrupting its ability to post videos or employ social media.  The reach of U.S. cyberweapons remain one of the military’s closest secrets, making it difficult to know how effective they would be against Islamic State’s decentralized propaganda campaign. The U.S. military is wary of deploying cyberweapons because once they are used, the Chinese and Russian military would get a good look and develop countermeasures, military officials have said.  U.S. lawmakers have pressured social media companies such as Twitter Inc. TWTR -0.19 % to close accounts used by Islamic State militants or supporters. The companies have moved to block these accounts, but militants can quickly open new ones using different personal information.  Pentagon officials say the current U.S. military strategy shows signs of success. They cite as examples the Kurdish offensive in Sinjar—which had been held by Islamic State—and the drone strike that killed Islamic State executioner known as “Jihadi John.”  To build on that progress, U.S. defense officials said, they have developed a series of so-called accelerants with the potential to advance the fight.  Pentagon planners, for example, are looking at potentially tripling the number of Special Operations Forces in Syria from the 50 the White House has said are headed there now.  The new teams would help arm the Syrian Arab Coalition, a loose group of Arab fighters who work closely with Kurdish forces in Syria.  The new approach is what one Pentagon official described as “drop, op and assess.” Ammunition is dropped, an operation is planned and conducted, and U.S. forces assess the performance of local fighters before providing them more ammunition.  After conversations with their French counterparts, some U.S. officials believe France would be willing to contribute some special forces, particularly if troops can be freed from Africa—a decision perhaps more difficult after Friday’s attack in Mali.  The fight against Islamic State in Iraq has its own unexpected roadblocks, including ones set by Baghdad. U.S. military officials say their Iraqi counterparts are blocking the deployment of Apache attack helicopters and the establishment of a base for American special operation forces to launch raids in Iraq and, potentially, in Syria.  The base would be used for “expeditionary targeting,” Pentagon jargon for teams of commandos assigned to hunt Islamic State leaders. The Iraqi officials opposed to the deployment of Apache helicopters and the new base are also against the return of American troops, U.S. officials said, because of worries of a domestic backlash, particularly from Shiite militia groups.  The U.S. also wants Iraq to appoint a new commander to oversee its war operations and serve as a counterpart to the new U.S. three-star commander, Lt. Gen. Sean MacFarland. U.S. officials say such an appointment would streamline efforts against Islamic State and make the Iraqis more focused and accountable.  Naseer Muneer, a spokesman for the Iraqi Defense Ministry, said Iraq and U.S. already work closely together. He disputed the idea that Iraqis were blocking the Apache helicopters and said no official request for a commando base had been made.  Military planners are looking at ways to increase the number of airstrikes against Islamic State by changing a policy to protect against civilian casualties in Islamic State-held territory. Currently, jets in the U.S.-led coalition won’t drop a bomb if the military believes there is any risk of accidentally killing civilians.  Easing this policy would open up more Islamic State targets for attack, officials said. But many military leaders believe it would alienate the very population the West needs to win to their side.  U.S. military officials say the overall changes under consideration so far are a refinement rather than a change in strategy against Islamic State.  “There is only one thing that is going to beat these guys and that is a ground army,” said a military official. “And there are only two ways to do that: provide one yourself or rely on someone else’s. It is either invade Syria or do what we are doing.”  —Damian Paletta contributed to this article.  Write to Julian E. Barnes at julian.barnes@wsj.com, Stephen Fidler at stephen.fidler@wsj.com, Gordon Lubold at Gordon.Lubold@wsj.com and Philip Shishkin at philip.shishkin@wsj.com  Islamic State killed a Chinese hostage. An earlier version of this article incorrectly specified that the militant group beheaded a Chinese hostage.
To prevail against ISIS, the West must settle on military tactics, cut off oil money and counter propaganda, strategists say.