This is what the U.S. Commander (Townsend) had to say on ISIS leaving for Palmyra...
http://www.liveleak.com/view?i=b89_1481779907
Calling the Syrians "Russian Proxies" was very calculating.
Is it not beyond the realms of probability that in this instance the U.S. used Daesh as their proxies? So many thousands of fighters and vehicles, traveling out of a combat zone across a desert, without being detected and countered? The excuse of being in Syria does not wash, it hasn't stopped operations there over the last few years.