President Obama and his inner circle of national security advisers appear conflicted about whether ISIS, the terrorist group also known as the Islamic State, poses a direct threat to the United States. Defense Secretary Chuck Hagel last week described it as “an imminent threat to every interest we have.” This week, Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, saw it as “a regional threat that will soon become a threat to the United States and Europe,” according to his spokesman, while State Department spokeswoman Jen Psaki said “we've not seen them focus” on planning “9/11-style attacks.”

While the administration sorts out its analysis, it should recall that the president's previous decisions did much to create the opportunity that ISIS seized so brutally. When Obama withdrew U.S. troops from Iraq in 2011 without a status of forces agreement, he left a power vacuum that the fanatics were only too eager to fill. An agreement would have kept a stabilizing American force in Iraq capable of dealing with the threat they posed.

Washington cannot now fulfill the obligations it incurred by invading Iraq in 2003 without engineering the destruction of ISIS.

As soon as American forces left, Iraq's Shiites persecuted their Sunni rivals, splitting their nation asunder. ISIS took advantage of Sunni loathing for, and fear of, Iraq's Shi'ite rulers to conquer large swaths of territory populated by welcoming co-religionists. Unsurprisingly, Sunnis often assisted the Islamic State in taking savage retribution against local minorities.

So Washington cannot now fulfill the obligations it incurred by invading Iraq in 2003 without engineering the destruction of ISIS. A full-scale re-invasion should not be necessary. Author and foreign affairs scholar Angelo Codevilla suggested recently in the Federalist that most of the military resources needed to do the job are already in the Middle East, in the hands of governments that know ISIS threatens their existence.

Obama must now put sufficient pressure on regional governments, especially governments that helped create the problem by funding ISIS in its war against the Syrian regime, to use those resources in a combined effort to eliminate ISIS.

Saudi Arabia, whose Grand Mufti Sheikh Abdulaziz Al al-Sheikh has condemned ISIS, owns several hundred fighter jets purchased from the United States and Britain. The same is true of other regional powers. With American assistance, they can meet what is probably a much greater threat to them than to America.

Meanwhile, as Codevilla suggests, the United States can pressure other governments to crack down, as American officials are, on those who fund the Islamic State's self-styled caliphate through cash transfers, smuggling, and black-market oil purchases. America's weary but too hasty scramble out of Iraq now obliges this nation's reluctant return to that battlefield.