In recent weeks, however, a wave of assassinations by al-Qaida in Iraq and by Shiite Muslim militiamen is threatening the American-paid tribal leaders and fighters of the Sunni Awakening Councils, which are at the heart of the reduced violence in some of the most dangerous places in Iraq.
The Awakening Councils and their Sunni sheiks have stopped the insurgent attacks on American troops in Anbar province and turned on the Sunni jihadists they'd sheltered for years.
This seismic shift virtually ended the violence in bloody Anbar and helped dampen the killings in Diyala province north of Baghdad and in some of the worst neighborhoods in the Iraqi capital. This and a six-month cease-fire by radical Shiite cleric Moqtada al-Sadr's Mahdi Army militia are far more responsible for the improved security in Iraq than is the temporary increase in American troops.
Assassinations of council leaders and sheiks, however, have spiked since Osama bin Laden called the 80,000 tribal volunteers ''traitors and infidels'' in a recent videotaped lecture.
Suicide bombers and ambushes have killed more than 100 Awakening Council leaders and several tribal sheiks, and that has American commanders worried. U.S. officials say they believe that Sunni militants have mounted most of the attacks, but that some have been carried out by Sadr's militia or by the Iranian-backed Badr Corps, which has close ties to Iraq's Shiite-led government.
The Sunni council members see it differently. They say the Shiite militias and their friends in the U.S.-backed Iraqi government of Prime Minister Nouri al-Maliki are the biggest threat to them, with al-Qaida in second place.
Either way, it's bad news for the American commanders, who've cooperated with their former Sunni enemies against the wishes of the Baghdad government and worked hard to spread the model to other areas where the Sunni extremists are strong.
The assassinations pose a serious threat of renewed violence if the Sunni groups do an about-face and resume their insurgency against Iraq's central government or, worse yet, begin fighting the Shiite militias and government forces as the United States tries to draw down its forces in Iraq to pre-surge levels.
The stated purpose of the American surge - sending 30,000 more U.S. troops to Iraq and bringing the total number there to 160,000 for a limited time - was to buy time and security so the Iraqi government could make some progress toward national reconciliation.
With virtually none of the Bush administration's political benchmarks achieved to date, U.S. officials have pointed to the Iraqi parliament's recent passage of a law that supposedly would roll back some of the worst effects of purging former members of Saddam Hussein's predominantly Sunni Baath Party from the government and the military.
Sunnis, however, now say the much-acclaimed new law does nothing of the sort and, in fact, will likely strip the few remaining Sunnis of their government jobs.
All of this underscores what every American military commander in Iraq has said over and over again - that there can be no U.S. military victory in Iraq, only a political solution among the Iraqi people. President Bush, however, has steadfastly ignored that good judgment in the pursuit of his impossible dream.
Recent developments also sound a cautionary note about the optimistic pronouncements by briefers in Baghdad and Washington about how al-Qaida in Iraq has been routed, is on the run, is licking its wounds, has been decimated and otherwise is in its last throes.
There's no question that the homegrown Iraqi chapter of al-Qaida has been hurt and driven back, but there also is no question that the Islamists are rebuilding, refitting and once again making their presence felt by attacking their former Sunni allies.
If the U.S. commanders can't find some way to shield their new Sunni friends from the death squads - both the Sunni militants and the Shiite militias - then a rising tide of violence will sweep away both the surge and the shaky calm it's brought.
* JOSEPH L. GALLOWAY s a military columnist for McClatchy Newspapers and a former senior military correspondent for Knight Ridder Newspapers.