Territory losses, military pressure, financial problems and poor management have crushed the morale of fighters and the jihadists are reportedly struggling to keep fighters' confidence.
According to a report by the United States military's think tank the Center for Combating Terrorism (CTC), now some militants are so disillusioned they are looking for any way they can to get out of the fighting, reported mirror.co.uk.
Much of the ISIS group's problems with personnel originate from their inability to pay wages.
According to a document released by Bayt al-Mal, the Treasury Ministry of ISIS, fighters now get the equivalent of just £100 (approx Rs 9600) a month because of "exceptional circumstances”.
In Iraq, Islamic State is feeling the pinch because it recently lost Ramadi and other territories.