The United States is stepping into its third Iraq war in 24 years. But if President Barack Obama has his way, this one will be fought under different rules.
In a speech at West Point last month, Obama outlined a new "light footprint" approach to fighting terrorist groups in the Muslim world, one that relies mostly on U.S.-supported local forces, not American troops.
The strategy, he explained, "expands our reach without sending forces that stretch our military thin or stir up local resentments."
The countries he had in mind, Obama said, were Yemen, Somalia, Libya, Mali and Syria. He barely even mentioned Iraq.
But now, thanks to the march toward Baghdad by ISIS, the Islamic State of Iraq and Syria, Obama's still-unfinished counter-terrorism strategy faces a real-world test sooner than anticipated.
Why is Obama, a president who won the White House by promising to get the United States out of Iraq, sending U.S. troops back in?
The president cited two reasons: the destabilizing effect of a civil war in a region that produces much of the world's oil, and the danger that ISIS could use territory it controls as a base for terrorism against the U.S.
But he put most of his emphasis on terrorism, and not only because that's a stronger selling point for war-weary American voters.
If there's an Obama Doctrine in foreign policy, it begins with one rule: no more large-scale military intervention. But the rule comes with a major exception: terrorism.
Obama withdrew U.S. troops from Iraq, is withdrawing from Afghanistan, and has repeatedly rejected proposals for using military force against the regime of Bashar Assad in Syria.