The US must fight a complex society to win a lasting peace in Iraq

Essentially the Americans have several difficult challenges before them. First, basic law and order and essential services. If the occupation cannot deliver these, many Iraqis might even consider that Saddam's dictatorship was preferable.

Second, the role of the Shia majority vis-à-vis the Sunni minority. The Shias were persecuted under Saddam; some at least will be looking to settle old scores. And, as is said in democratic politics, "they've got the numbers" - if they wish to use them and are allowed to.

Third, the complexity of the ethnic issues. The Kurds could be forgiven for never wanting to trust a regime in Baghdad again, but America's ally Turkey, and its non-ally Iran, have concerns about Kurdish bids for independence. Are the Kurds to be forced into an Iraqi Federation to placate the Turks? How much autonomy will they want, and how much can they be given?

Next, the overall sentiments of most Iraqis. Sunnis and Shias will likely jointly oppose the presence of Western occupiers or bases. Iraq is not a Western state. It is as secular as anywhere in its region, but it is foolish to expect a free Iraq to be a strong pro-Western state.

Finally, sorting out all of the above in a context where Iraqis have democratic rights, especially to a government of their choosing. If the US falls into the trap of installing a regime without popular support, the regime will last just as long as an army remains to sustain it.

Running Iraq without pressing the wrong local buttons is certainly going to be harder than conquering it proved to be. But after 1945, despite what must have then seemed daunting obstacles, the US managed the occupation, reconstruction and international rehabilitation of Japan with reasonable success. It remains to be seen if it can repeat that success in postwar Iraq.