To fulfill his vow to “destroy” the Islamic State of Iraq and al-Sham (ISIS), U.S. President Barack Obama will have to make a lengthy military commitment to Iraq and Syria. So far, however, the United States has limited its involvement to air strikes in Iraq and some military assistance to Iraqi and Kurdish forces on the ground. Obama’s speech this month also raised the prospect of air strikes in Syria.

Yet, within the halls of Western power, there are still those who regard using military force against ISIS as a mistake, believing that it will bolster the jihadists’ narrative of the West vs. Islam and aid ISIS propaganda -- especially if there are civilian casualties. In turn, ISIS will find it easier to recruit new members. For that reason, some have argued, ISIS was hoping to provoke a showdown with the United States all along.

Nothing could be further from the truth. Looking at the group’s recent history, it is clear that the last thing ISIS would want is for the United States to step up its military efforts in Iraq. After all, it was the U.S. military -- in conjunction with Sunni tribes -- that crushed the group’s emerging network in Iraq in late 2006 and early 2007. By 2008, the group's estimated 15,000 membership had been eviscerated by the death of 2,400 of its members and the capture of another 8,800. At the time of the U.S. troop withdrawal from Iraq in December 2011, the network now known as ISIS had between 800 and 1,000 members

Although the ongoing civil war in Syria may have reenergized ISIS, it was the U.S. withdrawal that really turned the group’s fortunes around. For example, with the U.S. departure, Iraqi special forces lost access to American intelligence and helicopter transportation, significantly diminishing their abilities to carry out nighttime counterterrorism operations. On the political side, Iraqi Prime Minister Nouri al-Maliki took the withdrawal as his cue to purge senior military figures whom the United States had trusted and replace them with vastly less competent loyalists. By October 2012, the Iraqi jihadist network had taken advantage of this to more than double in size and virtually double the amount of attacks it was carrying out a week.

That is why ISIS’ activities in Iraq -- particularly the beheadings of the American journalists James Foley and Steven Sotloff, which members of government, including Representative Adam Schiff (D-Cal.), a member of the House Intelligence Committee, have argued were meant to tempt Obama into action -- are really meant to deter the United States.

In the video of Foley’s beheading, for example, a British ISIS fighter suspected of carrying out the murder claims to be retaliating against U.S. bombing raids and the United States’ attempt “to deny the Muslims their rights of living in safety under the Islamic caliphate.” In the second video, Sotloff is made to ask whether U.S. citizens are interested in another war against ISIS having already “spent billions of U.S. taxpayers’ dollars and … lost thousands of our troops.” The British ISIS fighter warns governments looking to assist the United States to “back off and leave our people alone.” The video then cuts to an image of the British hostage, David Haines. These videos, understandably, did not lead to a change in Western policy, and Haines was killed next. The rhetoric in the video of his killing is similar to that in the Foley and Sotloff videos. The British ISIS fighter explicitly references how the Western military campaign in Iraq will lead to “another bloody and unwinnable war,” and that by continuing the fight against ISIS, the West will cause more British citizens to die. Alan Henning, another British man captured by ISIS, is identified as the next potential victim.

ISIS’ ideological forebears have used similar tactics with Western hostages. When American citizen Nicholas Berg and British citizen Kenneth Bigley were beheaded by Abu Musab al-Zarqawi’s network in 2004, Zarqawi was not trying to draw the United States and United Kingdom more deeply into the Iraq war. (There were already over 140,000 U.S. troops in Iraq at the time of Berg’s murder.) Rather, he was trying to weaken public support for the war and test whether the West had the stomach for this kind of fight. For example, prior to his death, Bigley was forced to read a statement saying that “Iraqis don't like foreign troops on their soil walking down the street with guns -- it's not right and it's not fair. We need to pull the troops out.”

ISIS also has a sound strategic reason for trying to deter further Western military escalation. Retaining and expanding its territory is the group’s main goal. The longer the caliphate endures, the more credible it seems and the more recruits it can attract. The end result of ramped up Western military action is likely to be the loss of much of ISIS’ territory and the collapse of its caliphate, shattering its image of strength and the inevitability of its advance. This was the case with al Qaeda franchises in Somalia, Yemen, and Mali in recent years. These groups, although not able to match ISIS in terms of numbers and ability to hold land, have all relinquished territory after military reverses. In other words, a new war would likely send ISIS back to where it was before 2014: it would be a security threat, especially to Iraq, but no longer a credible challenger to al Qaeda in terms of its reach and capacity.

In turn, if the West is serious about defeating ISIS, the group cannot be allowed to hold on to the territory it now controls. Local forces are not up to the task of reclaiming land from ISIS, and regional actors are showing little interest in intervention. Since ISIS is not going to give up without a fight, significant Western military involvement is required. Some argue that such involvement will increase the prospect of ISIS retribution in the West. Yet ISIS was a threat to the West long before American air strikes. Over the last decade, the group has been connected to multiple terrorist attacks in Europe, offered financial reward for the murder of European citizens, and was linked to a plan to transport chemical weapons into the West. Allowing its members control of a safe haven from which it could recruit and train new fighters only increases the threat that ISIS poses.

It is true that there will be unpleasant consequences for reengaging in Iraq. It would be naive to think there will no price to pay for taking on a terrorist army that is killing its enemies with impunity, controlling a significant territory in two strategically important countries, and whose fighters have a stated desire to kill Westerners. There is also an emerging consensus that any successful strategy to comprehensively weaken ISIS will take years -- a commitment for which public support is unclear.

None of this, however, means that avoiding conflict there will bolster Western security. By not acting, the West would be relying on the group to self-destruct. And that is too risky. For his part, Obama has shown a willingness to take military action, even though it means reversing his previous policies in Iraq and Syria. Yet there may be another reversal ahead. Obama has vowed to “destroy” ISIS without using ground troops in a combat role. These two things may yet prove mutually exclusive.