US and British forces stormed around Basra and al-Nasiriyah. Coalition expectations were high. These areas were occupied by second-rate Iraqi divisions, we knew. Many expected resistance would collapse quickly. And in these Shia areas, where Sunnis like Saddam Hussein were not popular, the Americans expected to be welcomed as liberators. In fact, initial resistance was minimal.

But since then, even in the areas through which coalition forces had penetrated, Iraqi resistance has reappeared and stiffened. Saddam is not fighting conventionally. He has allowed the initial heavy forces to penetrate Iraqi positions, and then his forces are shooting at the soft logistics and rear area vehicles.

He has shored up weak units with detachments of Republican Guards and Fedayin. Iraqi forces are shooting from buildings. Some of the soldiers are hiding among the civilian population. Others are actually covering their uniforms with civilian clothing and women and children have reportedly been pressed into service as human shields.

By the time the US and British forces arrive in the areas around Baghdad, the Iraqis will have taken our measure. They will have learnt that we are trying to fight with firepower rather than with our ground troops. They will recognise their vulnerabilities to US air power, the reluctance of the US forces to engage and risk hitting women and children, the porous US and British rear areas, and the lack of dismounted US infantry strength.

As we close the ring around Baghdad, the Iraqi tactics are also predictable. The Iraqis are defending in depth for miles around Baghdad. Three Republican Guard Divisions are there, plus the Special Republican Guard. The terrain is largely flat, but criss-crossed by rivers, canals, roads, embankments, and various settlements, villages and towns. More than five million people live there. The Iraqis’ advantages are knowledge of the terrain, willingness to take losses, and their ability to blend with the population. They have all the weapons they need to fight on an almost even basis if they can close in on US forces.

They will use smoke and oil fires to obscure visibility and counter US air power. Their tanks, no match for the M1A1 or Challenger in the open, are still formidable against troops and light vehicles, especially up close. Their rocket-propelled grenades will penetrate light armoured vehicles. Their heavy machineguns are effective against helicopters and low-flying aircraft. Their small arms are accurate, and lay down a heavy volume of fire. The Iraqis will want to fight close and dirty, with Iraqi tanks darting in and out of garages and buildings; they will conduct small-scale offensive actions with dismounted soldiers supported by mortars.

The fighting will be full of the tricks we have already seen and more: ambushes, fake surrenders, soldiers dressed as women, attacks on rear areas and command posts. The Iraqis will be prepared to conduct high-risk missions of a kind we would not consider.

The coalition will use its ground forces to fix Iraqi positions, but will do its best not to close on the ground. Instead we will rely on artillery, attack helicopters, A10s and Harriers to destroy the enemy once their locations are fixed. As we always say, what we can see, we can hit, and what we can hit, we can destroy.

We will advance carefully, with daily movements of a few miles or even a few hundred yards. We will drive corridors between Iraqi positions, to isolate and encircle them, and we will insert helicopter-borne and special operations forces into the Iraqi rear areas. As we clear the areas, we will establish careful defensive positions, with interlocking visibility and fires to guard against small-scale Iraqi penetrations.

And we will eventually, inevitably, have to engage in close combat. We do “own the night” with superior night-vision technology. We are very good, courageous and disciplined. We will “grind it out” if necessary.

Also, we will have to control the civilian population in the areas we have occupied. Many will leave their homes, and we will provide food and shelter, but we will do all this with the knowledge that among the population will be Iraqi agents and soldiers.

As the fighting enters Baghdad, we will try to organise resistance inside the city among the Shia population. And we will continue the campaign to destroy Iraqi command and control. Saddam, in turn, will have to consider whether to use his chemical and biological weapons.

Given our superiority, the ultimate outcome is not in doubt. But for how long, how much it will cost, and how much damage we inflict, depends on the Iraqis’ will to fight. We must do all we can to take it away as we close in to the critical battle of Baghdad.

• General Wesley Clark was Supreme Allied Commander Europe 1997-2000, and led Nato forces during the Kosovo campaign.

Times Recommends

• 'Great Schlep' may seal the deal for Obama
• Hindu 'storm troopers' flex their muscles
• Ahtisaari: deserved reward for (failed) plan