"America’s basic objective is clear: We must seek to destroy the Islamic State. It is simply not enough to block the group’s threat to the Kurds or other vulnerable minorities in the region. The risks of even a relatively small 'state' (or 'caliphate,' as they proclaim it) are chilling. Leaving the Islamic State in place and in control only of its current turf in Iraq and Syria (including northern-Iraqi hydrocarbon deposits and associated infrastructure) would make it viable economically and a fearsome refuge for terrorists of all sorts.
Just as Afghanistan’s Taliban gave al-Qaeda a base of operations to launch terrorist attacks culminating in 9/11, a similar result could follow if the Islamic State successfully erased and then redrew existing boundaries." — John R. Bolton, Former U.S. Ambassador to the United Nations