President Donald Trump's administration hopes that the U.S.-backed fight against Islamic State in its last foothold in northeastern Syria will end within months. But a top U.S. diplomat recently said American forces will remain to ensure the "enduring defeat" of the militant group.
While we have an interest in remaining in eastern Syria after defeating ISIL to push Iran out of Syria, remaining to keep ISIL defeated is a legitimate objective, too.
Syria was part of a jihadi pipeline flowing from the wider Islamice world into Iraq both before and during the Iraq War. And Assad encouraged jihadi growth in Syria during the civil war to de-legitimize the rebellion and scare the Hell out of his backers to stick with him despite the heavy casualties to keep him in power.
So Assad would clearly allow jihadis to head back to eastern Syria either through passivity by allowing a vacuum that jihadis would fill or as an active policy to get revenge on Turks, Kurds, Jordanians, and Iraqis (and America and the West).
And after walking away from the Iraq War in 2011 after defeating al Qaeda in Iraq by 2008, we actually did have to engage in Iraq War 2.0 to re-defeat jihadis in the form of ISIL which established a caliphate spanning Syrian and Iraqi territory, and then branched out into other areas like Libya, the Sahel, Sinai, and Afghanistan.
Iraq War 2.0 was initiated by President Obama in 2014 despite his vehement opposition to the Iraq War initiated (with bipartisan Congressional approval, if you've forgotten) and won by President Bush 43 despite growing opposition at home.
I'm hoping our memories are good enough that we will decide we don't want to risk an Iraq War 3.0 to defeat a regenerated jihadi force in the Iraq-Syria region.