This week, American troops start leaving Iraqi cities in compliance with both former President George W. Bush's negotiated start date for withdrawal and President Barack Obama's campaign pledge. Given Bush's profound commitment to succeed in Iraq, if he were still in office and if he judged such a scheduled removal of troops to be dangerous, he doubtlessly would have postponed the action -- just as he changed his strategy and ordered the surge against the advice of most of his government and most of Washington in 2007.

Yet it was that surge and the changed strategy designed and led by Gen. David Petraeus that left Iraq at noon Jan. 20 largely peaceful and on a steady march to a stable, friendly, representative government.

But in the past several weeks, a deep, if quietly expressed, concern has arisen on the part of some Iraqis and some U.S. military personnel that the removal of U.S. troops so soon is precipitous and seriously risks a return to the murderous sectarian conflict of 2004-07.

The withdrawal plan that our government is carrying out intends to reduce the current 130,000 American troops in Iraq, including about 24,000 in Baghdad, to 50,000 by the end of 2011 -- all of whom will be outside the cities and used only for training and U.S. force protection. Pursuant to that plan, about 24,000 troops in Baghdad have been moved outside the city already to secured locations, such as Joint Security stations Istiqlal, War Eagle and Ur and Camp Taji.

In the fortnight leading up to this week's troop withdrawals, bombings of a Shiite mosque in Kirkuk and in the Shiite slums of Sadr City have taken about 200 Iraqi lives. Presumably, those attacks were carried out by Sunnis, whose decision to cooperate with U.S. troops two years ago in the Sunni Awakening and with the Petraeus surge combined to form Bush's successful strategy to bring peace and victory to Iraq.

Now Sunnis are scared that the majority Shiite Iraqi government has just been waiting for the U.S troops to leave the cities so the Shiites can cut off the jobs to former Sunni fighters that the U.S. government promised. There are (not completely reliable) reports that the jobs cutoff and other abuses have started already.

It was the later strategy of the Bush team (and those of us who supported that strategy) for U.S. troop, diplomatic and economic presences to remain as long as needed at a high enough level to restrain the Shiite government from its natural tendency to abuse the Sunnis and push Sunnis to participate in government.

To the contrary, it was always the position of the anti-war advocates that only if U.S. troops left promptly could the Iraqis be forced to work together.

The Bush theory having been proved successful, we are about to test whether the alternative theory also can work. Will the Shiites and Sunnis (and Kurds) peaceably rise to the occasion or fall back into mass sectarian murder and civil war?

We all must hope for the success of the current U.S. administration's idealistic theory that Shiites and Sunnis already have overcome their historic murderous hatred of each other and are ready to govern and live together in peace. Far too many of our troops, allied Iraqi troops and innocent Iraqi citizens have been killed or distressingly wounded to now lose the peace so terribly earned. Continued...