THE question of whether a war will break out over Iran's nuclear programme has been around for so long that is easy to become almost blasé. In 2006, Israeli Prime Minister Benjamin Netanyahu was already asserting dramatically: "It's 1938 and Iran is Germany." This year, however, feels different. The threat of war is much more real. A conflict would begin with an Israeli bombing raid on Iran. But it would be likely swiftly to draw in the US - probably the UK and France, as well, and possibly the Gulf states and Saudi Arabia.

Israeli fears are driving the process. Israeli Defence Minister Ehud Barak has talked of Iran entering a "zone of immunity" - in which its nuclear programme becomes unstoppable - in the coming months. The Israelis are particularly concerned about plans to put Iran's uranium-enrichment facilities into hardened underground bunkers. US Defence Secretary Leon Panetta is said to believe there is a strong possibility of an Israeli attack in April, May or June.

But Israel is not the only factor. Saudi Arabia and the Gulf states are also obsessed by the need to prevent Iran getting nuclear weapons. President Barack Obama is still keen to avoid conflict. But in a presidential election year, it is harder for him to rein in Israel. The UK and France - the most important European military powers - are also seriously contemplating the prospect of conflict with Iran. Indeed, in contrast to the run-up to the Iraq war, the British and French are more bellicose than the Americans.

One European decision maker recently laid out the possible cycle of escalation and counter-escalation. Israel would mount a bombing raid on Iran's nuclear facilities. The US would not condemn the raid, while Europeans would halfheartedly speak out against the attack. When Iran retaliated against Israel, the Europeans and Americans would come to Israel's aid, with defensive measures: perhaps, initially, in the form of naval protection.

But it is also thought likely that Iranian retaliation would be aimed not just at Israel but also at western interests, and perhaps even at the Gulf states.

That would lead to a much wider conflict. US air power would be used to knock out Iranian retaliatory capacity. Any Iranian blockade of the Strait of Hormuz would be swiftly challenged by the US navy, with some token European support. While the Gulf states could never support an Israeli attack on Iran, they might get involved in this second round of military action - if Iran were foolish enough to attack them first. All the discussion is of the use of air and naval power. There is no appetite for sending ground troops.

Among some European decision makers, these steps are discussed with a calm that is slightly startling. So why the change in mood? There are several factors.

First, while Netanyahu is not liked or trusted by his counterparts in Washington, Paris and London, Israeli and Saudi concerns about the progress of Iran's nuclear programme are, to a significant extent, shared by their US and European counterparts.

Second, the success of the Libyan conflict has restored confidence in the effectiveness of air power. Advances in satellite and missile-guidance technology mean North Atlantic Treaty Organisation (Nato) air forces are now much more confident of their ability to hit the right targets.

Third, events have conspired to reduce the number of easy targets Iran can retaliate against. The British closed their embassy in Tehran late last year after it was ransacked by demonstrators. US troops have withdrawn from Iraq.

Fourth, the Saudis have made it clear that if Iran does acquire a bomb, Saudi Arabia will do the same. The Saudis are believed to have a deal with Pakistan, which is a nuclear-weapons state. The threat of a nuclear arms race loomed large in recent comments by British F oreign S ecretary William Hague.

Finally, with the Middle East in flux, some argue that it is important to strike a decisive blow against Iranian influence, before the country vastly strengthens its position by acquiring nuclear weapons.

If you listen to these arguments long enough, they almost begin to sound reasonable. But before the West slides into yet another armed conflict in the Middle East, the counter-arguments need to be urgently restated. The Iraq conflict demonstrated the risks of making decisions about war based on "intelligence" about weapons of mass destruction. It also showed that wars often develop in ways that politicians completely fail to anticipate.

Iran may not be able to retaliate effectively in Iraq - but it could hit Nato troops in Afghanistan, perhaps by providing the Taliban with anti-aircraft missiles.

The water supplies of the Gulf states are also vulnerable to attacks on desalination plants, as are their oil production facilities.

Finally, the delicate politics of the "Arab Spring" are a more powerful argument against attacking Iran than they are for launching an assault. Western military action, in alliance with Israel and against a Muslim country, would be a huge boost to militant Islamists.

None of this means that an attack on Iran's nuclear programme is unthinkable. But there is a dangerous lightness to the discussion. ©2012 The Financial Times Limited