Military Analysis: US and British troops are in the process of consolidating their foothold in Iraq, writes Tom Clonan.
Fighting will continue around Umm Qasr and Basra in order to secure their port access to southern Iraq. The security of the Al Faw peninsula is crucial to the re-supply and reinforcement necessary for the assault and capture of Baghdad.
In the coming days and weeks, this area will see the disembarkation of hundreds of thousands of tonnes of military equipment, armour, vehicles, weapons, fuel and ammunition. It will also become the entrepot for the humanitarian aid that will be necessary to support an Iraqi population in extremis.
To the north of Basra, US troops are fighting bitterly contested battles at Karbala, Najaf and Nassiriya.
These locations are of immense strategic value, consisting of river crossings situated on routes leading directly to the centre of Baghdad. Karbala and Nassiriya represent the left and right boundaries of a final assault designed to penetrate to the heart of Saddam's regime.
This front, roughly 120km wide, currently represents what the military refer to as the "forward edge of the battle area". To the rear of this newly formed forward edge, the US will be assembling a massive assault formation which will become the final piece of what the US terms its "mosaic of force".
This vast assault formation will consist of elements of the US 3rd Infantry Division (Mechanised), 7th Cavalry, 101st Airborne Division and the 82nd Airborne Division.
It will be reinforced by members of the 1st Cavalry Division, 1st Armoured Division, and the US 4th Infantry Division.
The concentration of ground troops in such large numbers is deemed necessary for urban warfare. The tactical doctrine for fighting in built-up areas refers to the scale of force required as "mass combat power".
The force required is calculated as follows. In what is called the "optimum combat correlation", the attacking force would ideally outnumber defenders to the order of 6:1.
Based on this estimate and based on the destruction of an enemy in an urban environment, military commanders would anticipate an "exchange ratio" of approximately 2:1.
This is military-speak for an anticipated casualty rate to the order of one allied death for every two Iraqi combat fatalities.
In 1998, the security studies programme based at the Massachusetts Institute of Technology applied this calculation to a simulated US invasion of Kuwait City. In this simulation, the city was occupied by a force of Republican Guard similar in number to that currently defending Baghdad.
The security studies programme concluded that in such an action, "several thousand American soldiers and marines would have been killed". If forced into urban combat in Baghdad, Gen Franks and his staff at Centcom will be facing the possibility of thousands of US combat deaths in the coming weeks. For America, this would represent combat losses of a scale and magnitude not seen since Vietnam.
Russia's recent experiences of urban warfare in the Chechen city of Grozny will provide ample food for thought for the Bush administration as it contemplates the invasion of Baghdad. The battlefield phenomena generated by street fighting in Chechnya would likely present themselves during a campaign of urban warfare in Baghdad.
There are striking similarities between Grozny and Baghdad. For example, Saddam's Republican Guard, equipped with the same weaponry as Chechen separatists in Grozny, might well mimic their modus operandi in the streets of Baghdad.
In this respect, there will be grave cause for concern amongst Centcom commanders. Gen Franks and his officers will be keenly aware of the effectiveness of former Soviet Union-produced weapon systems such as the ZSU 23-4 quad-mounted 23mm cannon used in the direct-fire role in city streets. In addition to anti-aircraft cannons, anti-aircraft multi-launch rocket systems such as the BM-21 MLRS would almost certainly be fired at point- blank range in Baghdad at advancing US troops.
The Iraqis have an abundance of such equipment. Almost useless in open desert against the air superiority of the allies, these low-tech weapons would form a formidable arsenal in the narrow alleys and back streets of Iraq's capital.
In addition to anti-aircraft weapons deployed in the direct fire role, T-72 tanks and heavy artillery pieces would be used in a similar way. In Grozny, the use of smoke and white phosphorous (WP) rounds was commonplace and comprised approximately one quarter of all ammunition expended. WP rounds would have a devastating effect on advancing US troops in Baghdad.
US troops would counter these threats with the maximum use of force and the exploitation of all available firepower.
This would be achieved through the concentration of "mass combat power" - of the order of that being assembled south of Baghdad.
If such force were to be applied in the indiscriminate manner required of high-intensity urban warfare in Baghdad, military casualties would be eclipsed by the certain destruction of the Iraqi capital and the annihilation of its citizens.
If Gen Franks and his commanders were to attempt low-intensity urban warfare with a slower rate of advance, the initiative in battle would be given to Baghdad's defenders.
Such a scenario would be unacceptable and would result in a costly and drawn-out battle for the capital.
In such circumstances, with summer approaching and daytime temperatures on the increase, the population of Baghdad, already in a vulnerable state, would be exposed to a humanitarian catastrophe.
Gen Franks and his commanders would eventually prevail in a campaign of urban warfare in Baghdad. As professional soldiers, however, they will be keen to avoid the scale of bloodshed and suffering such an assault would entail.
The coming days will see a continuation of the build-up of force south of Baghdad. There will also be a continuation and escalation of the air campaign.
The propaganda campaign will also intensify in an attempt to persuade the defenders of Baghdad of the futility and potentially tragic consequences of resistance.
• Dr Tom Clonan is a retired Army officer with experience in the Middle East and former Yugoslavia. He is a fellow of the US-based Inter-University Seminar on Armed Forces and Society. He currently lectures in the School of Media, DIT.