2) The Great Reconciliation between jihadist groups will begin

Much of the Obama administration’s anti-ISIS efforts have been trying to leverage other “vetted moderate” groups in Syria against ISIS, with some “smart set” thinkers even advocating engaging “moderate Al-Qaeda” to that end. We are already seeing jihadist groups gravitating towards ISIS, such as the announcement this week by Pakistani Taliban leaders pledging their allegiance to the Islamic State. Other groups of younger jihadis are breaking away from Al-Qaeda franchises in North Africa and defecting to ISIS. Despite bitter rivalries between ISIS and other jihadist groups in Syria, namely Al-Qaeda’s official Syrian affiliate Jabhat al-Nusra, these other groups will be hard-pressed to deny ISIS’ caliphate claims if they do take Baghdad. In that part of the world, nothing succeeds like success. If Baghdad falls, jihadist groups, some of whom have been openly hostile or remained neutral, will quickly align behind ISIS. And the horrid sound coming out of Washington, D.C., will be of foreign policy paradigms imploding.

3) What of U.S. personnel in Iraq?

The US Embassy in Baghdad is the largest embassy on the planet. And after Obama sent 350 more U.S. military personnel to guard the U.S. Embassy last month, there are now more than 1,100 US service members in Baghdad protecting the embassy and the airport. That doesn’t include embassy personnel, American aid workers, and reporters also in Baghdad. ISIS doesn’t have to capture the airport to prevent flights from taking off there (remember Hamas rockets from Gaza prompting the temporary closure of Israel’s Ben Gurion Airport this past summer). If flights can’t get out of Baghdad, how will the State Department and Pentagon evacuate U.S. personnel? An image like the last helicopter out of Saigon would be of considerable propaganda value to ISIS and other jihadist groups. Former CNN reporter Peter Arnett, who witnessed the fall of Saigon in April 1975, raised this possibility back in June. It’s not like the U.S. has prestige to spare internationally, and the fall of Baghdad will mark the beginning of the end of American influence in the Middle East, much like the case in Southest Asia in 1975.