From a piece by Johannes at TCS:
Since mid-2005, al Qaeda has aimed not to defeat the Coalition militarily, but to drain American public support politically. The strategy was forced on the insurgents by a string of failures in 2004 and 2005. The Baathist groups and their al Qaeda allies planned first to establish a geographic base of control within Iraq; second, to block Iraqi elections; and third, to prevent the establishment of the Iraqi Security Forces. They failed to achieve any of these goals.
The ensuing strategy was dictated by weakness. Mass killings of Shi'ite civilians - a tactic designed by Abu Musab Al-Zarqawi over the initial protests of the al Qaeda leadership - replaced military confrontation as the insurgency's operational focus. Civilian atrocity is, by definition, easy to implement, as it targets what is undefended. The strategy does nothing to "win hearts and minds." Support for al Qaeda has dwindled to under 2% among the Sunnis of Iraq; among other groups, it doesn't register at all. Nor can atrocities advance a political agenda, or control real estate.
But the mass killings were a boon to recruitment.
Read the whole thing.