There are a raft of extreme measures you could take with respect to Raqqa before nukes;
Bomb …
all access roads (so no exits)
electricity generation plats
water supplies
The issue is there are lots of people trapped in Raqqa who have nothing to do with IS and who are desperate to get out
The most likely solution is to have Russian and Iranian ground troops retake the city as part of their operation to restore control under Assad. The former Head of the UK military has suggested that the best option
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