Many of those attacks were orchestrated by al-Qaeda’s Iraqi affiliate, which in 2006 established the Islamic State of Iraq. After weakening in 2007 and 2008 (when the U.S. paid Sunni tribal leaders to fight jihadists), the Islamic State strengthened again as the Obama administration’s inattention allowed Iraq’s Shia prime minister, Nuri al-Maliki, to intensify his persecution of Sunnis. Then, after Syrians rebelled against Bashar al-Assad, the Islamic State expanded across Iraq’s western border into Syria, later renaming itself the Islamic State of Iraq and Syria.

Significantly, when the last American troops left Iraq, in December 2011, isis did not follow them home. “In its various incarnations,” notes Daniel Byman, a counterterrorism expert who is a professor at Georgetown, the Islamic State “focused first and foremost on its immediate theater of operations.” Although isis was happy if people inspired by its message struck Western targets, it made little effort to orchestrate such attacks. Research fellows at the Norwegian Defence Research Establishment detected only four isis-related plots in the West from January 2011 to May 2014.

But beginning in the fall of 2014, the number of isis-related plots in the West spiked. The Norwegian researchers counted 26 from July 2014 to June 2015 alone. What explains the rise? The most plausible explanation is that the Islamic State started targeting Western countries because they had started targeting it. In August 2014, the United States began bombing isis targets to protect the Yazidi religious sect in northern Iraq, which isis was threatening with extermination. France joined the air campaign the following month. Since then, isis seems to have moved from merely inspiring attacks against the West to actively planning them. November’s attacks in Paris, writes Byman, were the “first time that isis has devoted significant resources to a mass-casualty attack in Europe.” Afterward, isis released a video warning the people of France: “As long as you keep bombing you will not find peace.”

In the wake of the Paris attacks, the Republican presidential candidate Marco Rubio declared that the reason isis targets the West is “because we have freedom of speech, because we have diversity in our religious beliefs … because we’re a tolerant society.” Yet only weeks earlier, isis had downed a Russian airliner over the Sinai, thus targeting the distinctly intolerant regime of Vladimir Putin. The Islamic State’s justification for that attack was identical to the one it gave for its attack on France: It was bombing Russia because Russia had bombed it.

All of which suggests 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.” If the public reaction to Paris and the December attack in San Bernardino is any guide, continued jihadist terrorism will also lead to a rising demand for American ground troops. That, argues the French isis expert Jean-Pierre Filiu, would be the worst trap America could fall into, because isis wants to cast itself as the Islamic world’s defender against a new crusader invasion.