Given Sunni Arab support for the insurgency, the 2005 Iraqi constitution could only be achieved by a political compromise between the Shia Arab majority and the Kurdish minority in the north of the country. This arrangement begn to collapse in the second half of 2007 as the United States weaned the Sunni Arab minority away from the insurgency and began to move away from its previous support of the Shia Arabs and the Kurds.
By the end of 2007 the United States had armed a 70,000 strong Sunni Arab militia in formerly rebellious parts of Iraq, much to the concern of the Shia Arab government in Baghdad and the authorities in Iraqi Kurdistan. This American swing towards the Sunni Arabs was in part just the internal Iraqi aspect of a wider American rapprochement with Sunni Arab states in the region. In return for them joining an American-backed coalition to oppose the growing power of the Shia state of Iran, those states, including Saudi Arabia and other members of the Gulf Co-operation Council, were promised both a settlement of the Israel-Palestine question (still to be delivered) and a definite change in the US attitude to the Sunni Arab minority within Iraq.
This shift in the US position has understandably alarmed Iraq's Shia Arab majority, as it was probably intended to do. When it seemed likely that the USA would launch a military attack on Iran (an attack now at least postponed), the Americans were ready to neutralise possible Iraqi Shia military support for the Iranians by creating a Sunni Arab military counterweight within the country.
In many ways this American shift towards the Sunni Arab minority has been a reversion to the traditional power arrangement in Iraq. After the Ottoman Turkish sultans took the country away from the Iranians during the sixteenth century, they ensured Sunni rule over the majority Shia for the next four centuries. After the British took control of Iraq in 1917-18, they continued this political hegemony, installing a Sunni Arab monarch to rule the country. Even after the fall of the monarchy in 1958, the Sunni Arab minority - including Saddam Hussein and his Tikriti gang - continued to run Iraq. Only since 2003 has the Shia Arab majority achieved political dominance after centuries of oppression. Now those Shia fear that the United States may be going back on its commitment to democracy so as to further the interests of its allies in neighbouring Sunni Arab countries.
The Iraqi Kurds have traditionally been hostile to all Arabs, whether Sunni or Shia, but since 2003 it has been in their interest to ally with the Shia Arab majority, in part because this was what their American friends wanted. Now the amity between Iraqi Kurdistan and the United States is becoming increasingly strained. Despite US denials, American assistance to Turkish air attacks on PKK guerrillas in Iraqi Kurdistan during December 2007 has been patently obvious. For the moment Iraqi Kurds are prepared to overlook this rather than alienate the USA, their principal ally. However, if Turkish attacks continue, extreme Kurdish nationalists may well start hitting back at the Americans was well as the Turks. The continued postponement of the Kirkuk referendum is also increasing Kurdish hostility.
The Americans claim that the success of their 'surge' strategy in reducing the Sunni Arab insurgency in Iraq has produced an ideal opportunity for a general political settlement in that country. However, neither the Shia Arabs nor the Kurds seem in any mood to do favours for the USA and its new Sunni Arab friends in Iraq at the moment. One sign of this is the continued delay in passing a new Iraqi oil law which would benefit US energy companies. The Americans have certainly shifted the political kaleidoscope in Iraq, but the consequence seems unlikely to be the settlement they desire. Pursuing the Sunni Arab agenda in Iraq seems more likely to alienate old allies from the USA rather than win them to its cause.