David,

All good points, and I think I can argue we already failed strategically when we failed to find WMD, and changed the balance of power in the region in a way that favored both Iran and sunni extremists. The current approach may have been well intended, but the underlying assumption or hope that Iraq would step up politically and militarily hasn't happened.

Can we recover from failure? England did during WWII, as have others throughout history. My question for you is should the West fight IS regardless based on the threat the pose to us?