Those who supported the decision to go to war against Saddam Hussein in March 2003 may not now remember why they did so. I supported the war and, given the emergence of similar circumstances, would do so again. Mr. Hussein’s refusal to satisfy the outside powers that he no longer possessed weapons of mass destruction justified the use of force against him.

It is more than likely that the proven existence of WMD in the hands of rogue rulers will require force to be used again. Both America and Israel are clearly contemplating military action against Iran, which scarcely bothers to disguise that it has embarked on the production of weapons-grade uranium and already has missile delivery systems.

Yet it is not so much the specter of WMD that prompted my espousal of the war two years ago but the likely outcome of the war itself. In the teeth of those who warned of hard fighting and heavy casualties, of a Stalingrad-on-Tigris, I took the view that the war would be won quickly and cheaply at little cost in lives to either side.

As things turned out, those who made that judgment were proved right. Iraq’s armed forces were demolished and Mr. Hussein’s regime overthrown, at a cost of 150 coalition battle casualties, in a campaign that lasted only three weeks. Regarded solely as a military operation, the Iraq war of 2003 was a scintillating success. It is the aftermath that has sowed doubt among those who supported the decision to risk an attack.

Casualties among the Western forces have risen. Casualties among Iraqis have risen even higher and continue to rise; not, however, for the reasons foreseen by the anti-war party. It is not conventional force or conventional defense tactics that end lives, but something quite different, which may be called large-scale terrorism, largely by car bombing, suicide bombing and the assassination of Iraqis who cooperate with Westerners.

This is not a new development. What is going on in Iraq resembles the second Palestinian intifada, though it is more intensive and better organized. It is also more difficult to counter, since the Western forces lack the detailed intelligence to which the Israeli security forces have access.

Some critics of Western occupation policy are raising the idea that Iraq is becoming a Vietnam, a popular thought with old-style opponents of American foreign policy, but quite inaccurate. What America confronted in Vietnam was ideological nationalism, organized at several levels, political and military, all ultimately depending on the Viet Cong’s ability to defeat the enemy by conventional methods. There is absolutely no equivalent in Iraq of the Viet Cong main force and its battalions of highly motivated infantrymen.

It is important to understand that the violence in Iraq is not countrywide. Large areas are comparatively peaceful, including the whole of the Kurdish north and much of the Shia south, which is garrisoned mainly by the British.

The heartland of the trouble is in the center, in the so-called Sunni Triangle, west of Baghdad. Those who make the trouble are former Baath members, loyal to Mr. Hussein’s system, and unemployed officials, together with jihadis who enter the country from Syria and Saudi Arabia. They are supported financially by Islamic charities and are motivated by the neo-Islamic belief propagated by Sayyid Qutb, executed by Nasser in 1966. Qutb has been enormously influential in the Muslim world and is largely responsible for the rise of Al Qaeda. He preached that the decline of Islam from its rightful place in the world could be overcome only by setting aside the primacy of compassion as a value and indeed adopting the calls for jihad.

Jihad, he taught, could bring about the circumstances that would allow the restoration of the universal caliphate – hence Nasser’s hostility – and the subordination of the infidels to a new Islamic empire. The supporters of the neo-Islamic movements are known as Salafists and learn the importance of adopting strict piety and self-sacrifice, including if necessary the self-sacrifice of suicidal combat.

It is these religious, not ideological, beliefs that make the anti-Western forces in Iraq so difficult to deal with. Placing no value on their own lives, let alone the lives of those they revile, they are not susceptible to the usual methods of military control employed by Westerners, who presume that survival in combat is as important to their enemies as it is to themselves.

Since the American leaders – particularly the neo-conservatives who inaugurated the war – took it for granted that Western-style politics would readily take root in Iraq, if offered as an alternative to Mr. Hussein’s dictatorship once overthrown, religious terrorism baffles their approach.

Yet not altogether. Neo-Islamists are a minority, even in the most pious Muslim countries, and few Muslims, however devout, wish to die as suicide fighters. A majority of Muslims everywhere are familiar with what Western civilization offers and are eager to enjoy its rewards.

That explains in part the extensive opposition to the holding of the impending elections in Iraq. Successful elections and the establishment of a government bring a mandate that shakes the claims of even the most committed Islamists to enjoy the right to oppose its authority.

Such a government, properly supported by Western troops and money increasingly to be supplied by Iraq’s growing oil revenues, would hearten Iraq’s home-grown security forces, at present under attack from Islamist terrorists.

It would also dishearten the pragmatic opponents of democracy, of whom there are many, who, while assuming Islamic clothing, really fear that democracy will expose them for what they are: unreformed supporters of the old regime, in which a Sunni minority exercised power over the Shia majority.

Let us hope that the American believers in elections as the best cure for political trouble are proved right in Iraq, as they have usually been elsewhere.