The two most recent columns in this series have focused on the increasing tensions between the United States and Iran, evident in the belligerent statements coming out of Tehran and the even more sustained, hostile rhetoric emanating from the George W Bush administration and the neo-conservative wing of the Republican Party (see "Baghdad spin, Tehran war" [6 September 2007] and "Iran: war and surprise" [13 September 2007]).

Paul Rogers is professor of peace studies at Bradford University, northern England.

He has been writing a weekly column on global security on openDemocracy since 26 September 2001

On the American side, the political offensive has been accompanied by comments from the United States military and diplomatic leadership, not least General David Petraeus and Ryan Crocker's related criticisms of Iranian involvement in Iraq at the congressional hearings of 10-11 September 2007.

There are strong arguments that the warlike rhetoric aids the political leaderships on both sides in their respective domestic predicaments. The Iranian president, Mahmoud Ahmadinejad, has even been criticised within his own party for a cavalier attitude to inflation (now running at over 20%), while for his part Bush is widely seen as a lame-duck president. In these circumstances, the danger is that a febrile, antagonistic atmosphere reinforces a climate that could - quite possibly by accident - quickly escalate into war.

Indeed, even in the past week four additional developments have ratcheted up the tensions even further. In the context of the underlying balance of forces in the Persian Gulf region, make it necessary to analyse what would happen if there really was a war with Iran.

A spark, and a flame

The first development was the unexpected statement from France's foreign minister Bernard Kouchner that war with Iran could not be ruled out. Kouchner is one of Nicolas Sarkozy's appointees from the political left, and is routinely regarded as a foreign-policy liberal; his record includes advocacy of intervention on human-rights grounds in disaster-zones and "failed states". This context, and the fact that Kouchner's comment (misunderstood or not) no doubt reflects the views of his president, reinforces the sense that the French government is moving closer into line with the Bush administration - indeed, more so than Germany, Italy, Spain or even Britain.

France's motives may include an oil-related desire to improve relations with Washington; the French oil company, Total, is now linked with Chevron in plans to develop the Majnoun oilfield in southeast Iraq (see Pepe Escobar, "French-kissing the war on Iran", Asia Times, 18 September 2007). This is a potentially lucrative deal, but requires the acquiescence of the Iraqi parliament - and that is unlikely without American involvement.

The second development is the claim made by Iran that 600 of its Shihab-3 medium-range missiles are available to target United States forces in Iraq and selected sites in Israel (see "Response to pro-Zionists on Oct. 12'", Jerusalem Post, 17 September 2007).

The third development is Israel's enigmatic air-raid in northern Syria on 12 September (supplemented by the declaration on 19 September that it now considered Gaza an "enemy entity"). The Syrian raid is particularly worrying for Iran, less because it was directly affected but more because the response among Arab states (some of whom Iran has been attempting to cultivate) has been so muted. This at least suggests - and it must be a worry for Tehran - that whatever else might ensue if war does break out, there will be little regional support for Iran.

The fourth development is the convening by the Bush administration of a meeting of permanent members of the United Nations Security Council in Washington on 21 September directed against Iran. The principal aim is to intensify and strengthen the sanctions already in place against Iran on account of its nuclear-power programme; the US will also seek backing for its blacklisting of the Pasdaran-e Inqilab (Iranian Revolutionary Guards Corps) on the grounds that it supports terrorism.

This combination of events does not - any more than the pre-existing tensions outlined in the previous column in this series - mean that war between the United States and Iran is inevitable. It is the case, however, that public and media discourse in the US is moving in the direction of "preparing" citizens for that possibility. Such a situation opens out the field of potential dangers, among which is one or more relatively small incidents could precipitate a full-blown conflict.

Such an incident might be engineered by Israel, by US forces entering Iranian territory or waters, or (perhaps more likely) by radical elements within the Revolutionary Guards seeking to regain their diminishing status within Iranian society. If a crisis did develop rapidly to the point of major US air-strikes on Iranian targets, ultra-radicals on both sides would be delighted. For Washington's neo-conservatives, it would be a near-ultimate vindication. But what would happen when the balloons popped?

A war and its aftermath

A war with Iran, irrespective of how it started, would stretch well beyond a couple of days of strikes by US air-force and navy planes, and missiles against Iranian nuclear facilities (see "The next Iran war", 16 February 2006). There would also be attacks against four other sets of Iranian targets: air defences, air bases, missiles and command- and-control systems. Some of these would be targeted even before nuclear facilities were hit, partly to reduce the risk of US aircrew casualties (and hostages, a recurrent American nightmare in relation to Iran).

The US requirement to counter Iranian retaliation, especially by Revolutionary Guard units against Iraq and oil facilities in the western Gulf, means that its forces would have to attack numerous "forward bases" of the guard. This will involve a strenuous effort to severely damage transport and communications nodes, especially in western Iran; there could even be attempts to destroy the Iranian political leadership.

All these plans make operational sense from a strictly military standpoint, but two of their aspects are immediately apparent. The first is that the scale of the assault is such that it could not be completed within a few days. The combined US air force and navy might be formidable, but even this degree of force would be stretched to undertake hundreds of sorties stretching over many days; repeated reconnaissance, including bomb-damage assessments in between the raids; many repeat operations; and improvised reactions to setbacks, accidents or unexpected events. It would be clear, almost from the start, that this would not be over within a week.

In addition to his weekly openDemocracy column, Paul Rogers writes an international security monthly briefing for the Oxford Research Group; for details, click here

Paul Rogers's latest book is Global Security and the War on Terror: Elite Power and the Illusion of Control (Routledge, July 2007). This is a collection of papers and essays written over the last twenty years, with two new essays on the current global predicament

The second aspect is the mismatch that would soon appear between early appearance and underlying reality. It is highly likely that the early indications from a sustained US military operation against Iran would be of a crippling of Iranian military power and of serious damage to its nuclear programme. America, in other words, would appear to have "won" this brief war. This, however, would be an even greater illusion than the three-week race to Baghdad in March-April 2003. It is highly unlikely that, however much wishful thinking there might be to this effect in Washington, the governance of Iran will fall apart at the seams - let alone evacuate the scene to social collapse and implosion, as happened in Iraq.

What is far more probable on the Iranian side is that the Revolutionary Guards would be revitalised to spearhead a vigorous campaign in Iraq, and to back retaliation against US allies in the western Gulf (including strikes against their oil facilities). This strategy might evolve over many weeks or even months - just as in Iraq four months passed between the termination of the Saddam Hussein regime and the first big indication of the war that was unfolding, the bombing of the United Nations headquarters in Baghdad in August 2003.

It is also as certain as can be that the Iranians would seek every means possible to speed the development of nuclear weapons. These two processes - Iran's deepening involvement in Iraq and its intensified nuclear programme - would in turn provoke further US military action, involving both the deployment of ground forces across the border from Iraq and repeated air-raids.

There is more. As a war with Iran escalated, the impact on the al-Qaida movement would be galvanising. Al-Qaida might have little or no affinity for Shi'a Iran but the Islamic identity of the republic would in the midst of war against the "great satan" transcend confessional differences. Islam would be under renewed attack in a new theatre of war, and that war would moreover be covered in great depth by the regional satellite news-channels with their commanding, engaged audiences across the middle east and beyond.

A perilous moment

This is only the rudimentary outline of the broad, probable consequences of a United States war with Iran. There must be many more detailed calculations available to strategists in the Pentagon and military colleges across the US. But whether the Pentagon or openDemocracy is the preferred source, this sketch is already enough to indicate why many among the US military - as well as senior figures in the US state department - are strongly opposed to the idea of an escalating conflict with Iran.

Such internal dissent over the drive to war also means that a sudden, large-scale attack by the United States on Iran remains unlikely. What becomes more plausible by the week is that a spark might start a conflagration - a war not entirely by accident but not by direct design either. And once it started, there would be little prospect of turning back.

In this dangerous environment, it may be that international leadership is the best hope of leading a process that offers a route away from confrontation. Amid the feverish rhetoric, almost the only actor who is championing the diplomatic option and cooling the temperature is Mohamed ElBaradei, director of the International Atomic Energy Agency (IAEA). ElBaradei's initiative in securing agreement with Iran on 27 August 2007 over a timetable for resolving the disputed nuclear issues provoked intense opposition among leading western states, but it may represent the basis of a way forward. It will need to find support among the political power-brokers if this perilous moment is not to end in another devastating war.