In 2016, Donald Trump, then a candidate for president, described Barack Obama as the “founder of ISIS.” In the end, it may be Mr. Trump who comes to be known not as the terrorist group’s founder, but as its savior.

The Islamic State has been weakened considerably since its peak in 2015, when it controlled a territory the size of Britain, but the Trump administration’s targeted killing of Maj. Gen. Qassim Suleimani may have poised the group for a comeback. Just as the misguided American invasion of Iraq in 2003 revitalized Al Qaeda, some 17 years later, a return to chaos in the same country may yet do the same for the Islamic State.

Granted, the White House was correct to identify General Suleimani, the leader of Iran’s Quds Force, as an enemy of the United States. Using the militia groups he cultivated and controlled, he was responsible for the deaths of hundreds of coalition soldiers in the late 2000s and early 2010s. But war in the Middle East is nothing if not complex; General Suleimani’s proxies also indirectly served American interests by fighting the Islamic State — to great effect.

Still, contrary to the breathless eulogies to him in Iran, he was not some indispensable hero who single-handedly defeated the Islamic State. Other commanders will fill his shoes, if not in star power then at least in strategic expertise. The real boon for the jihadists will be the second-order effects of his death.