At the heart of the military machine

From outside, the two anonymous aircraft hangars are identical. Painted grey and brown, they face each other in the heart of a sprawling military camp in the Qatari desert, divided over 100 metres by an empty, concrete-block road. Inside each are two strategic control hubs, the military nerve centres from which US and British commanders will run the war in Iraq.

From here General Tommy Franks and his British counterpart Air Marshal Brian Burridge will follow their troops on the ground, at sea and in the air and assess the latest satellite photos and intelligence. They study the risk of chemical and biological attacks and plan and re-plan for every contingency as the battle progresses.

Perhaps better than anything else in the vast military operation about to unfold in the Gulf these buildings reveal the subtle differences between the two countries.

The US joint operations centre in the centre of the 106 hectare (262 acre) compound at Camp As Sayliya is a mini-Pentagon. Built over several months at vast expense it is littered with technology and bravado, half Hollywood set, half computer game. A few months ago it was a small part of an obscure US military supply depot sitting in the rubble-strewn desert 30 minutes' drive outside the Qatari capital Doha.

Now the cramped, low-ceilinged room boasts six large plasma display screens, where commanders will watch their forces in battle depicted as small blue and green icons. It should enable "real-time" decisions on how to move troops and which new targets to hit. Information comes from spy plane and satellite pictures as well as the hundreds of global-positioning devices carried by military units.

Captured Iraqi maps from the Gulf war have added to the detail. Long gone are the Gulf war maps of old, with drawing pins and lines of string marking troop positions and enemy camps. The Pentagon boasts of its new hi-tech warfare, run through a highly secure intranet which should allow commanders at the frontline to send emails direct to Gen Franks, who will be sitting in his prefabricated office 700 hundred miles south of Iraq. Gen Franks and his fellow commanders can in turn email out instructions for soldiers on the ground and air tasking orders for pilots.

"Instead of taking out my sledgehammer I can take out a target more subtly," said Colonel Steven Pennington, who runs air operations from inside the centre.

Television screens in the corner remind the men and women on duty that war is just hours away. They must be nervous, but let little of it show.

"I'd like you to send a message to your prime minister, Mr Tony Blair. Everyone at central command would like to buy him a beer," one US officer said.

Across the road is the British joint operating centre, the rubber-floored room from which Air Marshal Burridge and a team of around 300 staff will have strategic command over the 45,000 British forces taking part in the war.

The room was built in five weeks at the end of last year and feels distinctly workaday. A horseshoe arrangement of desks is set up around a large map table of Iraq and its neighbouring countries. In the main room a muted television sits in the corner and a projector screen hangs on the wall. There are dozens of laptops spread over the tables and piles of discarded classified documents marked for shredding. But there is none of the Pentagon's tech-heavy plasma screens or piped muzak. The mood is good-humoured and informal."We work on a very personal approach to issues," said Lieutenant-Colonel Richard Spencer, a Royal Marines officer involved in coordinating operations. The equipment appears more modest but is sophisticated and versatile enough to enable Air Marshal Burridge "to talk up, down and sideways".

He stresses the importance of "influencing the coalition": keeping in constant contact with the US operations centre and plotting the battle together. Behind him on the wall are three clocks marking the three time zones by which the commanders operate in Florida, the usual home of the US central command, London and Iraq. Each zone has its own codeword: Tampa (Romeo), UK (Zulu) and local (Charlie).

Security is paramount. Mobile phones are not permitted inside the room and entry is forbidden to most. Signs everywhere warn staff to exercise discretion. "Don't talk work at the swimming pool," says one. "Don't talk work beyond this point," says another by the exit.

Far from being anxious about the war, some of the officers sound jealous of their colleagues on the frontlines in the deserts of Kuwait. Lieutenant Mike Carty, 21, spent several weeks in Afghanistan last year with Royal Marines 45 Commando in operations to hunt down al-Qaida and Taliban fighters. Now his fellow marines are in Kuwait preparing to advance into Iraq, while he is sitting in Qatar handling supplies, logistics and soldiers' medical needs. "It is really frustrating not being able to be there," he said yesterday. "They are having a harder time of it and they don't have some of the luxuries that we have here, but I'd still prefer to be with them."

The centre fell silent as Air Marshal Burridge walked out of his small office, known as room D43, into the main hall yesterday. The joint operations centre, he said, is "where the rubber meets the road".

"We deal here with the world as it is, not as one might want it to be," he said. "We are physically and mentally attuned for war. I am very much hoping that right now Saddam is looking for his passport. It is the option that is right to take.

"If he doesn't, yes, we will be at war."