Karbala Gap holds the key to Allies' march on capital

The first frontal battles between US troops and Republican Guards could happen this weekend – though military experts believe the Battle for Baghdad proper may be several weeks away.

Senior Allied officers predicted yesterday an imminent battle between the US Third Infantry division and the Medina and Hammurabi divisions of Republican Guards for control of the Karbala Gap, a strip of land 25 miles wide (16km) which is the key to the approach to the Iraqi capital from the south-west.

US Air Force and RAF planes pounded the Guards positions for a second day yesterday as 20,000 US troops and their tanks moved up the west bank of the Euphrates river from Najaf, apparently preparing for an attack.

General Mike Jackson, Chief of the British General Staff, said: "The conventional fight ... with the Republican Guard is not too far away, I suspect."

Senior US commanders in the field have also told American correspondents that the Karbala Gap – described as "the last stepping-stone to Baghdad" – would be their next objective. Military experts counselled scepticism, warning that the military briefings may be intended to confuse the Iraqis and that the first blow could fall elsewhere.

In any case, the experts said, the US was unlikely to launch its main assault on Baghdad until the first armoured reinforcements arrived from the US in two to three weeks' time. The US has only 40,000 to 50,000 fighting troops south of Baghdad and relatively little armour (although total air superiority).

Some form of early victory over the Republican Guards would, however, be of immense propaganda value to the Allies in their attempts to calm jittery opinion at home and convince Iraqis that the Saddam Hussein regime is doomed. The capture of the Karbala Gap, a densely populated strip of marshes and farmland between the Euphrates and Lake Razaza, would give the Americans command of the plains south of Baghdad.

Fierce fighting continued yesterday much further south, around Nasiriyah, and to the east, near Diwaniyah, as US Marines came under attack once again from flying columns of Iraqi "irregular" troops, seeking to harass supply lines and slow the American advance. Four US Marines were reported missing after fighting near Nasiriyah.

The Marines are engaged in "blue-collar warfare," said Lieutenant Colonel BP McCoy, commanding officer of the Marine 3rd Battery, 4th Regiment. "There's no magic solution to it. It is just the hard-grinding work of patrols."

At least one American was reported killed in fighting and two marines died after they were run over by one of their own vehicles as they slept.

Most units of the US Third Infantry Division were said to be well north of the town of Najaf, advancing towards Karbala, which is only 50 miles from the capital.

"The Karbala Gap is the most direct route to Baghdad," a senior US officer told The New York Times. "It is a choke point. Once we go through, it allows us more freedom of movement between Karbala and Najaf. Once through, we have more effective range for weapons. It allows us to target or monitor the Medina and Hammurabi divisions and allows us to cover Baghdad itself."

Such open talk about military plans caused some experts to express scepticism. The verbal concentration on Karbala may be an attempt to confuse, they suggested.

Other US military sources indicated, however, that they thought that the Gap itself was relatively lightly defended and that the Guards were dug in mostly in the plains beyond. The US might therefore be building up the importance of Karbala in the expectation of a relatively easy advance.

The problem – as elsewhere – may be the holy city of Karbala itself (the site of the death of Imam Hussein, a Shia martyr and grandson of the prophet Mohammed). US troops by-passed cities further south, such as Nasirayha and Najaf, only to find themselves under constant attack from flying columns of Iraqi irregular troops, secret police and conscripted civilians.

The strength of the Republican Guards divisions defending the Gap is unclear. Each division has around 15,000 men. Elements of both divisions, regarded as the best in the Iraqi army, are thought to be positioned elsewhere. They have been under constant attack from the air – sandstorms permitting – for six days. According to one US intelligence report, desertions and transfers of Guards to stiffen other units may have reduced their strength to 60 per cent.