Q&A: Battle for Iraq

With coalition forces pushing towards Baghdad the BBC's defence correspondent Jonathan Marcus, at Central Command Headquarters in Qatar, answers questions about the war so far and the pitfalls ahead.

What does the Iraqi strategy appear to be for defending Baghdad?

The Iraqis are pursuing rather an interesting strategy. They have got their main defensive forces - the Republican Guard - arranged in a ring around the southern part of the city and obviously there are some Republican Guard units to the north as well.

But what we have seen over the last few days is the very dramatic use of lightly armed troops. We have seen this in Basra and Nasiriya, where a number of irregular formations are fighting a sort of guerrilla war against the Americans and the British.

We have also seen the use of these light troops further north, and in a major skirmish with the 7th Cavalry on the eastern bank of the Euphrates River.

It is interesting because the Iraqis are not engaging in large scale manoeuvre warfare - they know they will get defeated very quickly if they do that. They have kept their large formations pretty static.

We are expecting the American 3rd Infantry Division advancing north around Karbala to crash into the Iraqi Republican Guard's Medina division. I think that is going to be the first major set piece engagement of this war.

How exposed are the Iraqi forces positioned around Baghdad?

Obviously any large armoured formation in the field is very vulnerable to air power. And it is air power which is the great "force multiplier" for this US and British force - which is a relatively small force of combat troops for the task of invading a large country like Iraq.

The Iraqis will have tried to disperse their vehicles as far as possible. But they are probably not going to be able to move around very much because of that US and British air power.

So, in a sense, where the Iraqi positions were placed at the beginning of this war is pretty well where they are going to remain. Once they are attacked by the Americans, they may be forced back - it is once they start redeploying that you can actually hit them from the air.

A real crucial factor in all of this is to get the better weather so that you can actually have close air support and helicopter formations. At the moment the weather is just not suitable for that sort of thing.

What happens if Iraqi units withdraw back into Baghdad itself?

If British and US troops actually get to the gates of Baghdad before the regime has crumbled, then they have problems.

They clearly do not want to go into the city in any great degree of force. It could be very costly, in terms of both military and civilian lives.

Things could start moving very quickly once the weather clears - but there is a danger that you could end up with a sort of stalemate, with US forces arranged around the outskirts of Baghdad.

Will US and British troops be able to open a northern front?

The war plan initially had a major American division - the 4th Infantry Division - coming through Turkey down into northern Iraq, that would clearly have fixed the Republican Guard positions that were there.

But that division was not allowed to go through Turkey.

The Americans are putting relatively light forces into Kurdish areas in northern Iraq. So that too could be a factor which could slow things down and possibly enable the Iraqis to reposition forces in the north.

But once again air power could come into play. We believe the Turks are going to allow the Americans to use their air space - if not their air bases.

How much of a factor is the bad weather?

It is a huge factor for a number of reasons. First of all for mobility of helicopters. The 101st Airborne Division is called an air assault division in the American military. It does not have armoured personal carriers or tanks. It has transport helicopters like the Black Hawk, and attack helicopters like the Apache.

None of these have been flying at the moment because of the weather. So that is clearly delaying their arrival on the battle front.

The other factor is limited visibility as the supply columns grind their way up northwards. It is a little like driving through a snow blizzard.

This slow progress is a problem in security terms. There are reports of people falling asleep at the wheel.

Is Saddam Hussein is still able to communicate with his troops?

It is very difficult to say. We hear various US spokesmen talking about "degrading" communications. They claim the Iraqis are having problems with commander control. But there is no suggestion at the moment that communication has simply collapsed.

Republican Guard divisions are much closer to the Iraqi capital and one would imagine that they are fully in contact with their headquarters.

As far as the fighting elsewhere - Basra or Nasiriya for example - I think Iraqi forces there do not need to be under any centralised command. Basically their job was to stay behind and emerge once the initial American thrust had gone through.

Their fighting style is guerrilla warfare.

They do seem to be highly motivated - not least because they are very much identified with Saddam Hussein's regime.