General Martin Dempsey vs. John McCain on this:

[freshwest]

...(General) Dempsey, an Iraq veteran, has long been sceptical of US military involvement in the Syrian conflict, citing among other reasons the threat to US pilots from dictator Bashar al-Assad’s air defences. He has frustrated those who advocated American involvement in the two neighbouring wars, such as hawkish Republican senator John McCain, who in June called on Obama to fire Dempsey, saying he “has done nothing but invent ways for us not to be engaged.”

Echoing the White House’s stated position, Dempsey said the US needed “a coalition in the region that takes on the task of defeating Isis over time,” something the administration this week has put effort into broadening and strengthening. But the group’s ultimate defeat, the general said, would only come “when it is rejected by the over 20 million disenfranchised Sunnis that happen to reside between Damascus and Baghdad.”

http://www.theguardian.com/world/2014/aug/21/isis-us-military-iraq-strikes-threat-apocalyptic/print

While no doubt not all of the 20 million displaced people support ISIS, that is a significant number of refugees. And is why this isn't going away any time soon. And no, I don't: