They have gained ground, but terrorizing your own people is going to have a downside. This isn’t sitting behind the line and picking off deserters either. I do think it’s unhealthy the way this group is being portrayed in the news, like they are some great unstoppable force. I imagine war involves a fair amount of psychology, and seeing the enemy realistically seems important. I don’t abide romanticizing this bunch, I mean, now we have Ben Carson telling us we should be more like ISIS?! With all due respect, Ben, get a grip!
The Red Army did OK in the 40’s by executing the unsuccessful. The Italian Army practiced decimation right up to World War I. If a unit was thought to have failed in its mission, every hundredth guy in the unit was executed.