Since the Iraqi army melted away in the face of Islamic State onslaughts this spring, it would be overly optimistic to believe that a simple change of central government in Baghdad will rejuvenate it. Years of betrayal and cronyism by the government of Nouri al-Maliki created much acrimony and mistrust. To address this problem, Prime Minister Haider al-Abadi, with the support of Obama, has proposed a national guard force to complement the main army. It will be recruited, trained and employed locally — allowing Iraqis to fight for their own homeland on a province-by-province basis.

This is a good idea. It is also a daunting proposition. At present, an Iraqi national guard does not even exist, yet it will be a linchpin of the new strategy. While it is being built, the Islamic State may become nearly as entrenched in the nation as al-Qaeda in Iraq, its precursor, was in 2007. A hard fight lies ahead.

To succeed, U.S. advisers will probably have to help these new national guard units, as well as reconstituted regular army units, far beyond calling in airstrikes. Iraqis need to regain their unit cohesion, their political commitment to the state and their trust in each other. U.S. advisers, many of whom know Iraqis well from shared experiences over the past decade, are well-placed to help. Among other daunting challenges, Shiite leaders in Baghdad will have to persuade themselves that the new Sunni formations in the guard do not threaten the central government, and they must resource them adequately to take the fight to the Islamic State.