Tens of thousands of US and British soldiers are poised to start the journey from Kuwait to Baghdad and beyond, to the oilfields in northern Iraq.
In the original war plan, commanders could have assumed a simultaneous thrust south, from Turkey, but politics have eliminated that option.
This greatly complicates the operational planning. Not only will the Kuwait assembly areas need to be protected even more, but the logistics of such an extended line need careful consideration.
The public tends to focus on high-tech weaponry, and the leading combat units. Yet none will work unless the operators are given food and water, and the equipment has fuel, lubricants and ammunition.
Logistics often feel like the Cinderella part of military activity, but no soldier, sailor or airman can fight without a reliable supply line.
Pushing an armored division forward over a long distance is like trying to build a pyramid. You need a much larger base line to support the sharp point at the top.
In the Falklands conflict, it took a cascade of 21 air-to-air refuelling aircraft to put one Vulcan bomber over Port Stanley and return it safely to Ascension Island.
The army talks of the importance of lines of communication. These are the arteries from which the fighting units draw their sustenance as they advance.
In the Cold War, NATO forces in Germany did not envisage advancing much at all in the event of war. They could therefore ensure that their supplies were ready in position.
In the last Gulf war, the ground advance was fast but lasted for only 100 hours and then stopped. Even then, keeping the fuel tankers up with the frontline was demanding.
This time we are considering the possibility of sustained high-intensity fighting in Baghdad, with the main supply base in Kuwait.
* Food and water is as important to a fighting unit as guns and bullets.
* Logistics helps coordinate military units with a supply chain that keeps it moving.
* Refugees will also have to be dealt with by logistics command and unit leaders will have to decide whether to stop and help or race onwards.
* During the Falklands war, British bombers had to refuel 21 times before reaching the Falkland Isles.
* An advancing column is only as fast as its slowest component, meaning fast-moving US tanks will have to wait for slower refueling trucks and supply vehicles.
This will require fast work in setting up forward logistics areas along the route. These will need to be in secure areas, and that means more troops to guard fuel, ammunition, food and water storage dumps. The resupply routes will also need to be well protected.
None of this is that difficult given sufficient time and troops. However, shock and awe is by design short of both. The aim is rapid advance, and the plan uses fewer troops than a decade ago.
Dealing with refugees and prisoners of war is another logistics problem which can eat up manpower. We can predict some difficult decisions for the commanders as they progress northward.
There will be a reluctance to stretch the lines of communication too far. To be separated from resupply, and run the risk of running out of fuel, ammunition or water is not wise. Yet if the advance is as easy as is hoped, there will be great pressure to get to Baghdad as soon as possible.
To some extent tactical air transport and helicopters will be able to help in the forward area, but they are always in demand. In this war, they are likely to be allocated primarily for troop transport to urgent tasks such as taking the oilfields and any known chemical-weapon storage sites.
The US hopes to be able to use airfields in the northern Kurdish enclave to provide access. Planners will worry about the security here, given the mix of Turks, Iraqis and Kurds with odd insurgents.
Months of detailed planning will have gone into making sure that the logistic supply plan can work. It will also have to take into account what happens if a key supply dump is lost to Iraqi or terrorist action.
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