If you've been following any sort of news at all, you're probably familiar with the US taking credit for the ongoing siege of Mosul (it's really just the Peshmerga and Iraqi Army doing the heavy lifting). The city has been cut off from supply lines and a large-scale effort is currently underway to drive ISIS out of the city.
You may not be familiar with the US announcement that they're currently in planning stages for a similar attack on Raqqa, in Syria. Like a drunk man breaking into your house, pissing in your closet and then getting angry at you for supposedly 'looking at his dick', the US has announced their invasion plans and precluded Russia and Syria from participating in any form - the only two groups that have any legal basis to operate in the country militarily.
Extreme exceptionalism and bizarre detachment from reality aside, they have publicly stated that they intend for the operation to run (at least partially) parallel to the current siege of Mosul. This is equal parts peculiar and bothering.
It's unclear how they plan on purging the city, if it is actually their goal. The two local groups with soldiers on the ground that the US is able to influence are the Kurds and what they deem the 'Free Syrian Army', 'New Syrian Army', 'moderate rebels'... Their names change so often that it's probably best just to refer to them as what they are - sponsored jihadists.
The Kurds are presently in no position to provide a substantial ground force - they're locked up in fiights with Turkish incursions to the north aimed at stopping them from unifying.
The sponsored Jihadists aren't likely to provide much assistance - since the majority of US-supported groups swear allegiance to Al Nusra (the US directly sponsoring the group they blame for the September 11 attacks, who'd've thought) they'd potentially be willing to attack ISIS' positions in Raqqa to take as their own, but they've demonstrated many times recently that they don't care much for the US 'invaders', even though they do keep taking the free cash and weapons without complaint. Further, due to political maneuvering related to the Kurds, Turkey is likely to use it's (much greater) influence among the Jihadists to call them off.
The disturbing part is, coincidentally, more interesting.
Prior to, and in the early days of the Mosul siege, there were substantial reports circulating that the US had organised with ISIS leaders to force 9000 or so fighters out of the city, eastwards to reinforce jihadists in Syria. This would serve a few purposes - it'd make the Iraqi advance much easier, it'd preserve US 'terror assets' and it'd open up another front against the SAA troops attacking Aleppo. This is not as far-fetched as the media would have you believe - the US came to a similar agreement with ISIS when the Iraqi army approached Fallujah - during the attack, they were to quietly evacuate their more valuable personnel and equipment out of the city. Unluckily for them, their exit convoys were spotted by Iraqi scout helicopters. Iraqi command called the US to ask what the fuck was going on, and they got the response that they were not to attack the convoy for fear of civilian casualties. Iraqi command told them NO DEAL and sent several gunships to rip them apart. Once it'd become obvious the convoys were being obliterated, the US ordered Iraq to cease attacks because they were going to launch their own long-range airstrikes - another chunk of the convoy was destroyed, but if I recall correctly at least 50% escaped.
This exodus has not happened in Mosul so far - assuming the rumour is true, it's likely because the US has little ground-presence and would be unable to stop the Iraqis and Peshmerga from pulverising ISIS on the way out if they were to spot the convoys again.
It's from this perspective that the proposed attack on Raqqa is troubling. If the US have control over who enters and exits both 'gateway' cities, both large hubs for ISIS and related groups, it makes tactical sense to find a way to transfer power (ie. manpower, weapons, research into chemical agents, etc.) from the city that MUST be liberated (Mosul) to Syria, which they are still determined to undermine.
I don't know exactly how this is going to play out, but I can guarantee you the overlap period between the Mosul and Raqqa operations is not an accident or coincidence.
