After initial resistance, troops continued advance towards Umm Qasr
The BBC's Adam Mynott sent this report for BBC News Online from the southern Iraqi port of Umm Qasr.
Many of the young US Marines aged between 19-24 had been told to expect fairly light resistance from Iraqi forces as they crossed the border with the intention of taking the southern Iraqi port of Umm Qasr.
But when they crossed, shortly after dawn, through the wide gap cut in the sand reinforcement by 26 Armoured Engineer Squadron of British soldiers, they encountered much stiffer opposition than they had been expecting.
Initially small arms fire was aimed at the front of the convoy of more than 20 vehicles, then mortars were also fired in the direction of the convoy.
The commanding officer of Fox Company, Captain Rick Crevier, called up British artillery, which was stationed in northern Kuwait, just behind the border to target the Iraqi post.
I ran back as fast as I could towards the Iraq-Kuwait border as artillery shells burst overhead
Several volleys appeared to hit the Iraqi positions; some also fell close to US Marines who immediately conducted a hurried and somewhat chaotic withdrawal.
I ran back as fast as I could towards the Iraq-Kuwait border as artillery shells burst overhead.
The US Marines regrouped and Captain Crevier also called forward two M1-Abraham American tanks to try to help punch a hole through the Iraqi resistance.
The armoured convoy eventually got moving after three or four hours and made its way towards the port of Umm Qasr.
On the way, around 30 Iraqis surrendered to American forces, holding their hands up and waving white flags.
They are being held in custody and are being given food and water by US Marines.
Umm Qasr remains in a state of some flux.
There are still pockets of Iraqi resistance within the town, somewhere between the new port and the old port in Umm Qasr.
The new port is vital in the coalition's plans to bring humanitarian aid into the country.
At the moment, large amounts of aid are stored on ships in the Persian Gulf waiting to come into Umm Qasr.
US Marines fear that the waters in the port may have been mined - and that clearance operation will have to take place first.
Umm Qasr is the only deep-water port in Iraq.
It is where around 3,500 tonnes of food and humanitarian aid has arrived every day in the past decade or more, in the UN-organised oil-for-food operation.