According to a number of measures, their ranks are beginning to thin amid defections that have had the result - among other things - of forcing them to understaff their formerly robust checkpoints.
Near Kirkuk in the last week, 90 Islamic State fighters laid down their arms and turned themselves over to Kurdish peshmerga forces, Warren said. The former fighters were local men who had been coerced into joining the jihadists and have grown disillusioned with the cause or simply saw a way to quit the fight by turning themselves in.
To date, an estimated 23,000 brave Da'esh fighters have gone to meet Allah; not counting those who've managed to blow themselves up. They still have as many as 30,000 on hand, however, and they're continuing to successfully recruit.