Who is really fighting ISIS? In Iraq and Syria, ISIS faces Kurdish forces, the Iraqi Army and the Western air forces supporting it, and the Syrian Army and its allies from Hizbollah, Iran, and Russia. The Kurds of Rojava have been fighting for survival, and while outgunned, they have both political and military preparation, and something to fight for. They have been successful in their battles with ISIS, even though they have suffered immensely in the process.
The Iraqi Army? ISIS's spectacular rise coincided with the Iraqi Army's collapse. To understand this, as with so much about ISIS, it is necessary to look back at the early days of the US occupation of Iraq in 2003, when the decision was taken to disband the Iraqi Army that had existed under Saddam Hussein and create a new one. The old army had training, organization, most of their weapons, and had just reached the point of having nothing to lose. Many of them joined the insurgency against the US. Among those who did, many were killed, many were tortured and killed, and many survived. Some of those survivors, now battle-hardened veterans, are now part of ISIS. One of those who made his way through the US prison system in Iraq is ISIS's leader. These veterans, joined by al-Qaeda fighters, with Saudi and Qatari funding, and Turkish help getting across the border, have become ISIS, the force that controls a big part of Iraq and dominates and absorbs all other opposition forces in Syria.