Stats from CNN

From a CNN email:
ISIS, the terror group that calls itself the Islamic State, "can muster between 20,000 and 31,500 fighters across Iraq and Syria," a CIA spokesman tells CNN. That is two to three times more than the 10,000 fighters previously estimated by the CIA."

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If these numbers are correct - that would be equivelant to 2-4 US Army Divisions.

If the US did send boots - WITH THE INTENTION OF UNCONDITIONAL SURRENDER - how many Divisions should the US Military send?