Switcheroo

Back in the day, as you'll recall, the reason we couldn't leave
Iraq was that if we did, the (Sunni) insurgents would overthrow the
(Shiite) government. These days, though, the reason we can't leave Iraq
is that (government-backed) Shiite militias will kill Sunni civilians. Does anyone recall when this switch happened? Any guess as to how long before our new wonderful Anbar policy causes the worry to switch back?