When the book is closed on the Middle Eastern caliphate established this summer by the ISIS terrorist group, historians may view Aug. 19, 2014, as the turning point in this monster’s existence. That was the day ISIS disseminated its video of the beheading of American photojournalist James Foley.

Foley had spent years as a freelancer, bravely documenting wars for Western audiences. He was kidnapped by loyalist forces during the Libyan civil war and lived to tell the tale. Sadly, he fell into the merciless hands of ISIS, the self-styled “knights of Islam,” two years ago in Syria.

These monsters behead little children, make women their sex slaves and crucify young men.

ISIS hoped that its latest atrocity would intimidate Americans, especially this nation’s president, from taking further military action against it. For better or worse – and almost certainly worse for ISIS – it has badly misread the American people and, we trust, the American president as well.

Given the 2003 U.S. invasion of Saddam Hussein’s crumbling domain, the bloody years of occupation that followed and more recent events in Baghdad, Americans have been wary of re-engaging in Iraq in any way. U.S. public opinion has been so averse to the idea that President Obama had to promise that the United States would not get too deeply involved while backing up humanitarian efforts to aid Iraqi Christians, Yazidis and Kurds trying to escape the genocide that is the distinguishing characteristic of ISIS.

Then, despite the ISIS image of invincibility as it swept into Iraq from Syria, a few dozen U.S. airstrikes enabled Kurdish and Iraqi soldiers to retake the Mosul Dam. So ISIS responded the only way terrorists know, with an atrocity and a warning of more crimes against humanity to come, commencing with the threat to murder another American journalist held captive in Syria, Steven Sotloff: “The life of this American citizen, Obama, depends on your next decision.”

Perhaps ISIS jumped to conclusions after seeing Obama trade five terrorists back to the Taliban – two of them wanted by the United Nations for war crimes – in return for the captured U.S. Army Sgt. Bowe Bergdahl. After all, if a single American life is worth so much, ISIS terrorists may have reasoned, then posting a horrendous video of the grisly murder of an American will strike sufficient fear in Obama to make him stop the bombing.

We hope the administration does not fall into this trap. All Americans have seen enough to know that ISIS is a terrible threat to civilized people everywhere. These monsters behead little children, make women their sex slaves and crucify young men. It’s the same evil that murdered another American journalist, the Wall Street Journal’s Daniel Pearl, in 2002. Then the evil was called al Qaeda. Today, it’s ISIS. But only the names have changed.

Obama's decision is clear: These crimes against humanity summon all civilized nations, most of all the pre-eminent nation among them, to combine military and moral force to help destroy ISIS.