Every battlefield is also a humanitarian field, even after the fighting stops. To ensure a lasting defeat and prevent an “ISIS 2.0” requires all elements of our collective national power.
Initiating and maintaining stabilization activities are essential. If citizens cannot return to normal life in communities cleared of explosives and debris, then those conditions that initially allowed ISIS to take root return.
We walked away from defeating Saddam in 1991 after ejecting him from his Kuwait conquest (for some valid reasons, it is true) and found out what a joy it was to have a hostile terror-supporting Iraqi state under Saddam.
We walked away from Iraq in 2011 after overthrowing Saddam in 2003 and defeated various Syrian- and Iranian-backed terrorists and insurgents of the Sunni and Shia variety by 2008. And we experienced the joy of seeing an ISIL terrorist state rise up in Iraqi territory in the first half of 2014; and the joy of seeing Iran increase its influence in Iran to fight that terrorist-state threat.
Now that ISIL has lost their territorial hold in Iraq with our help in Iraq War 2.0, we need to remain in Iraq to leverage our increased influence to help keep jihadis out of Iraq, develop democracy and rule of law in Iraq, and to push Iran out.
Otherwise we might again see a terrorist state in Iraq or even an actual terrorist-supporting state again.