The US-backed Syrian Democratic Forces (SDF) have been attempting to break the ISIS defense in the Old Raqqah area in the city of Raqqah. An intense fighting is ongoing.
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Military Situation In Syrian City Of Raqqah On July 14, 2017 (Map Update)
If SDF forces are stretched, then it seem reasonable to think IS lines are stretched too.
I do not know if the SDF has deployable reserves in or near Raqqah, but if they have and think IS is stretched, they might be considering a large attack where there hasn’t been any fighting the last few days. They will then either find very thinly manned IS lines of will draw IS away from other positions and can attack there too. They need to find a place to break through IS lines, not just push them back. The first will cost the SDF more at the moment, but will save many afterwards.