On 19 December 1944 Eisenhower convened a commanders' conference to consider how to respond the the Ardennes Offensive the Germans had launched three days before. All was doom and gloom until George Pattoon took the floor. He said, 'The Kraut has stuck his head into a meat-grinder and my hand is on the crank.'
Patton had recognised that the German breakthrough was an opportunity as well as a threat.
Likewise, when ISIS advanced from Mosul on Baghdad, they stuck their heads into a meat-grinder, with the Kurds' hands on the crank.
The difference is that, while Patton was determined to turn that crank, it is not clear what the Kurds will do. After all, what reason has Nuri al-Maliki given them to pull his chestnuts from the fire? So the Peshmerga has occupied Kirkuk and other disputed areas around the margins of the KAR, but made no offensive move against ISIS. They have even stopped short of an attempt to take Mosul, probably calculating that it is too big, with too many different factions, some of whom would welcome them, but others of whom would not.
The last, best hope, though, for preserving a united Iraq, though, is a Kurd-Shia alliance. But even at this juncture, Maliki, despite having his back against the wall, is not reading the handwriting on it. Divisively sectarian to the last, he is still looking for a Shia solution, and at last report had not even spoken to Barzani since the fall of Mosul.
That Shia solution, a people's army of Shia militia fighters, is likely to defend Baghdad and the Shia south, but is unlikely to regain significant Sunni territory, and still less likely to pacify any territory it does regain. So as things are unfolding, the Peshmerga sit in Kirkuk, the Shia hold Baghdad, and, e voila, Iraq is partitioned.
If the U.S. still wishes a united Iraq, the best thing it can do now is provide logistical and tactical air support for a Peshmerga raid aimed at taking ISIS forces advancing on Baghdad in the rear. One swift stroke to destroy or disperse ISIS forces, and withdraw -- any attempt by the Kurds to hold Sunni territory would end in disaster.
This would require the U.S. and Maliki to concede more to the Kurds than they wish, but probably no more than the Kurds will take in the course of current trends.
The Iraqi army is a corpse, and any plan based on them will fail. By 2011, the Americans could just about claim to have built an army for Iraq, but since then, reduced training, flourishing corruption, and promotions and command assignments based on sectarian loyalties instead of professional competence, it has been all downhill. Soldiers enlist because it is better than being unemployed, and with no training, no leadership, and a nightmare trying to maintain the sophisticated weapons the Americans gave them (the beauty of the Peshmerga's old Soviet tanks is that they can be maintained in the shade tree garage; not so the Iraqi army's M-1s), what do you expect? It is really just the Job Corps in HUMMVEEs.
The KRG position appears to be that if Baghdad cannot provide security it should not claim sovereignty. The Kurds have come a long since 1991, when friends who dealt with them in Operation Provide Comfort found them a frustratingly quarrelsome gang of mountain-men. They have used the autonomy they have had to learn to conduct their own politics and order their own affairs. Now they stand at a historic moment, on the threshold of their dream of an independent state. When one compares the KAR to the rest of Iraq, I am not too sure I see a reason to fear that.
ISIS, on the other had, will not be a big winner in the end, It is only the most notorious of a number of Sunni factions who currently cooperate out of hatred for the Maliki government, but which will, in due course, turn on each other, and I expect we shall then see that ISIS does not represent the aspirations of a majority of Iraqi Sunnis.