The Generals declared that ISIS has recaptured Palmyra.
My guess is that ISIS retreated to Palmyra
where they may have a weapons cache
and the logistics would be more favorable for them.
Furthermore, it is to be noted that ISIS just walked in to Palmyra.
Palmyra is also a site which is still full
of historic artifacts, and as such may not come
under bombings by the Syrians.
It is also closer to the Iraqi border, and may then serve
as a base for the ISIS in Iraq in case
these are forced to retreat.
Should all the terrorist forces be concentrated
on Palmyra, expect a last ditch battle.