Weekly Standard explains:
IN 2004 AND 2005, BAATHIST AND SUNNI nationalist insurgent groups comprised the bulk of the resistance movement in Iraq. These groups weren't necessarily waging a sectarian war, nor did they espouse a particularly radical religious creed. By late 2005, a number of secular and nationalist groups had decided to join the political process--which is traditionally how insurgencies are ended. Some Sunni insurgent groups even provided voters with protection against AQI during the December 2005 constitutional referendum. Alarmed, Zarqawi ordered the February 22, 2006, bombing of the Askariya mosque in Samarra. Askariya's importance to the Shia community was underscored by Iraqi vice president Adel Abdul Mahdi, who likened the mosque attack to 9/11.
This single bombing dramatically reshaped the entire insurgency. Shia reprisals were swift, devastating, and largely indiscriminate. These mass sectarian killings shattered the Baathist and nationalist insurgent factions. For rank-and-file Sunni insurgents, witnessing bloody attacks orchestrated by Shias made al Qaeda's sectarian arguments seem sensible for the first time. Today, the violence caused by the remaining nationalist groups is negligible compared to that caused by AQI: intelligence sources confirm that AQI and its ideological compatriot Ansar al-Sunnah are responsible for the vast majority of violence on the Sunni side. The most significant nationalist faction is the Islamic Army of Iraq--although even that ex-Baathist group now purports to have embraced a radical Islamic ideology.
Trying to cope with the Shia anger is now the key. Despite the fact that the jihadis are killing the most, the Shias remain key to winning this war. If we lose the support of most Shias, there is little point to staying in Iraq since we liberated the Shias from Saddam's yoke in the first place. We are trying to get a democracy in Iraq for the larger fight against Islamo-fascism, but we can't shield the Sunni Arabs from their own stupidity much longer. We cannot do so to the extent that the Shias see us as protecting the former Sunni oppressers (and current bombers) at the expense of the Shias. To keep the Shias, we'll have to go to the 80% solution (or Plan B) that focuses on crushing and expelling the Sunni Arabs:
Sunnis will suffer under a winning dirty strategy, no question, but so far they've refused to accept that they're a minority. They will have to do so eventually, one way or another. And, eventually, Iraq will achieve political equilibrium. Civil wars do end. The losers lose and have to knuckle under. As my Congressional source says, "every civil war is a political struggle. The center of this struggle is for control of the Shiite community. Wherever the Shiites go, is where Iraq will go. So, the quicker we back the winning side, the quicker the war ends. ... Winning dirty isn't attractive, but it sure beats losing."
Much depends on whether the Sunni Arabs can feel safe enough from Shia vengeance to surrender and turn on the jihadis to defeat them in a united effort that finally earns the Sunni Arabs a little credit after decades of abuse under Saddam and four years of Sunni Arab terrorism.
That is what the surge is all about. And there are signs this is starting to work despite the continuing violence.
We're trying to win clean. This has the most hope of contributing to a larger victory. But we can win dirty, too, though it might only be a local victory. Funny enough, this alternative applies to the wider war on terror, too.