President Trump tweeted Friday that the U.S. “military has hit ISIS ‘much harder’ over the last two days” because of the group’s claim of responsibility for this week’s terrorist attack in New York that killed eight people.

“They will pay a big price for every attack on us!” Trump said.

The tweet coincides with the Syrian military’s capture of the city of Deir al-Zour, whose location near the border with Iraq, and surrounding oil fields, made it a strategic asset for ISIS. The group, which in 2014 controlled a contiguous area in Iraq and Syria that by some estimates was roughly the size of Tennessee (or South Korea), is now fighting for its life. It has lost Raqqa, its self-proclaimed capital in Syria; Mosul, the second-largest Iraqi city; and Hawija, the Iraqi city it had controlled for three years until last month. What ISIS hasn’t lost, though, is the ability to inspire people around the world to commit acts of terrorism. At its peak, the group carried out high-profile attacks in France, Belgium, and elsewhere. Attacks still occur, albeit less regularly—but many of these attacks bear few signs that ISIS “central” had anything directly to do with them except inspire the attacker into killing civilians.

Sayfullo Saipov, the 29-year-old Uzbek man who came to the U.S. in 2010 through the diversity-visa lottery, said he was acting at ISIS’s behest when he drove his truck into pedestrians on Tuesday. (ISIS claimed responsibility Friday for the attack.) The same is true of the attacker in Barcelona who used a similar tactic to target pedestrians in August, as well as the one who did the same in London in June. (My colleague Uri Friedman has written about how vehicular attacks are being used frequently as a low-cost and effective means of terrorism.) The fact that the Islamic State entity based in Syria and Iraq didn’t directly commit these attacks, but “inspired” the attackers to act on its behalf, shows that even if the U.S., its allies, and its adversaries who are fighting ISIS defeat the group, that doesn’t make the ideology go away.

Then there is the other problem. ISIS is now confined to a sliver of territory that straddles the Iraq-Syria border, and Iraqi forces on one side and Syrian forces on the other are closing in on the group (though it is said to have an active presence in Libya and the Philippines). The Syrian military, backed by Russian aircraft and Iranian fighters, captured Deir al-Zour with relative ease. They will soon turn their attention to other areas controlled by the group. In Iraq, the military, backed by its U.S. allies, has mostly pushed ISIS out of the country. At this rate, the U.S.-led coalitions and Russian-backed Syrian military will, to quote former Defense Secretary Donald Rumsfeld’s remarks about Afghanistan, “run out of targets” to hit, Trump’s tweets notwithstanding.

U.S. aircraft have indeed bombed ISIS targets in Iraq and Syria since the New York attack, the U.S. military said. The military’s statement said the action “further limits the group’s ability to project terror and conduct external operations throughout the region and the rest of the world.” But it’s not entirely clear that using strikes in Iraq and Syria to retaliate against a terrorist attack in the United States will necessarily yield results. After the attacks in Paris in November 2015, the French military bombarded the Islamic State’s capital of Raqqa, but that did not stop the subsequent the Bastille Day attack in Nice in 2016, in which 86 people were killed when the attacker drove his truck into pedestrians celebrating the occasion.

In March 2016, Peter Beinart wrote in The Atlantic that ISIS attacks in the West began only after the U.S. began targeting the group’s assets in Iraq in August 2014 in order to protect the Yazidi religious sect. (Beinart does not argue against humanitarian intervention.) He suggested that “the more America intensifies its war against ISIS, the more ISIS will try to strike Americans. And the more terrorism ISIS manages to carry out, the more fiercely America will escalate its air attacks, thus creating the civilian casualties that, according to the International Crisis Group’s Noah Bonsey, ‘tremendously help the narrative of a jihadi group like the Islamic State.’”

Which brings us back to Trump’s pledge that ISIS will “pay a big price for every attack on us!” With fewer ISIS targets left, it’s not clear what the U.S. or its allies can do stop the terrorist group’s ability to inspire individuals in the West and elsewhere through its online propaganda. The bombs might continue to fall in the Middle East, but, as the New York City attack showed, all it takes is one man in a truck who is prepared to kill innocent people for his cause.