The US is only adding a small number of special forces. These will be used to rescue hostages (when convenient) and the occasional arrest of an ISIS commander.
The US has no interest in going to war with ISIS as shown by the Russians and French finding a target rich environment for their own bombing raids.
The US is using ISIS to weaken Assad. If Assad falls, the US will then use al Nusra to suppress ISIS.
"Of course, blowback always happens except this time it is different, so we promise it won't. Lottsa love, The CIA."
