Air raid is a taste of what Baghdad may face

More than 100 US and British aircraft attacked Iraqi air installations last week in the biggest raid for more than three years. With the war drums beating louder in Washington and London, that might seem to indicate that further military action is imminent. But an assault aimed at ousting Saddam Hussein's regime cannot be mounted overnight.

In 1991 it took six months of preparation and half a million men (and a small number of women) to drive Iraqi forces from Kuwait. Going on to Baghdad to effect "regime change" – an option rejected 11 years ago by George Bush's father – is in many ways a much tougher assignment.

So far not one of Iraq's neighbours has signed up for military action, though Kuwait, Qatar and other small Gulf states are sure to fall into line. Saudi Arabia, however, has refused to allow the use of its territory, depriving the Pentagon of the ability to keep Iraq guessing where a ground attack might come from.

A three-pronged assault from Kuwait, Turkey and Jordan is being discussed, but even if the last two can be persuaded – particularly difficult for Jordan, given its volatile Palestinian majority – all three have short borders with Iraq. Jordan may be crucial, however, for another reason: the need to keep Israel out of the war.

Dennis Gormley, a consultant senior fellow at the International Institute for Strategic Studies (IISS) in London, said one of the first objectives of an invasion might be to seize territory in western Iraq and push President Saddam's scud launchers out of range of Israel. It could be significant that last week's raid was on Baghdad's main air headquarters in the west.

Military observers are working on the assumption that in a second Gulf war, the force to be assembled would be only half as big as last time. By the end of this month enough armour and helicopters are expected to be in place for a force of about 90,000, but it would take until early next year to bring in the weaponry and supplies needed for the 250,000 troops envisioned in leaked invasion plans.

The 1991 ground war was preceded by a month of bombing, and the same can be expected this time, preparing the way for a possible invasion around February, when the ground dry enough for armoured vehicles to penetrate the marshes of southern Iraq on their way to Baghdad. Unlike Afghanistan, the US and Britain would have to do nearly all of the fighting themselves.

And that fighting could be bitter. This time President Saddam is not expected to scatter his forces in the desert, where they can be annihilated from the air. Instead he is reported to have ordered resistance in the cities so as to drag out the conflict.

"If I were him," said Mr Gormley, "I would be telling the Republican Guard to bed down in urban areas, near shrines, hospitals – anywhere collateral damage might be a concern. They have the ability to deliver chemical weapons at short range. Street fighting would severely limit the technological superiority of US and British troops, and if they are forced to don chemical garb, it would reduce their effectiveness by 30 to 40 per cent."

There are reports that Baghdad is already making such preparations, planting iron rods and barbed wire to hamper paratroopers. The aim would be to inflict the same humiliation that US forces suffered in the streets of Mogadishu in Somalia.

Some planners, seeking to avoid a long build-up of conventional forces, have proposed lightning strikes by mobile forces to seize Baghdad and a few other key cities, cutting the regime off from most of the country. Known as the "outside-in" option, it is based on the hope that the Iraqi population would co-operate as soon as it knew it was safe from Saddam, but most consider it far too risky.

Long before there is any ground fighting, however, Britain and the US would be sure to do as much damage as possible from the air, where the biggest technological advances have been made since 1991.

"The planners are almost certain to begin with intensive bombing, aimed at encouraging defections and breaking the will of the Republican Guard," said Mr Gormley. "The military will count on a huge softening-up, with ground forces being brought in simply to administer the coup de grâce."