The militant group has been pushing the idea that the Taliban's "Islamic Emirate of Afghanistan is home for all Afghans".
The Panjshir Valley's resistance - right on the doorstep of the capital - is a blow to this particular image of unity.
On social media, hashtags voicing support for the resistance have begun to pop up.
The Taliban and the NRF have been negotiating but, although both sides say they are keen to avoid war, there has been no settlement reached, and it seems talks have given way to open fighting.
The Taliban say they have sent hundreds of fighters, but Panjshir is ready. According to news agency AFP, Taliban fighters who make it to the edges of the valley will be greeted by machine gun nests, mortars and surveillance posts fortified with sandbags.
Both sides say they have inflicted casualties, but exact numbers are difficult to gauge. Claims by the Taliban that they have taken control of certain areas have also been dismissed by NRF.
The Taliban are also reportedly trying to cut supply lines into the valley, potentially hoping to force the resistance to give up.