US forces have whatever equipment is needed to defeat any enemy on the field of battle. The key to success in war, however, is how to use the technology available.

The campaign in Afghanistan revealed flexibility and tactical skill on the part of US commanders in using the weaponry at their disposal. Though fighting a disorganised and ill-equipped enemy, they used resourcefulness they had not needed for decades.

The fact that they were able to do so underlined the depth of US military might. After the last two defence budgets, which together add more than $70bn (£48bn) to annual spending, it will become even greater. This raises a fundamental issue for other countries, both hostile and friendly: you cannot fight against the US, but you will not be able to fight alongside it either.

Donald Rumsfeld, the defence secretary, waxed lyrical about special forces soldiers on horseback in Afghanistan, taking part in cavalry charges while transmitting co-ordinates of targets to be hit from the air by precision weapons. "The 19th century met the 21st century," he said.

The activities of a small number of special forces soldiers decisively improved US ability to hit Taliban targets. But it was no spur-of-the-moment tactic. Beneath each element of that capability lay an elaborate infrastructure.

Special forces are highly trained and have their own weapons and equipment, including modified aircraft, all of which had to be transported quickly to Afghanistan. So too did the rescue teams, with their helicopters, who would rapidly extract them if they got into difficulties.

The aircraft circling above them, carrying satellite-guided bombs possessed only by the US, also had to reach Afghanistan within weeks of the September 11 attacks on the US. Those carrying offensive weapons had no nearby bases available. B-1 and B-52 bombers flew from Diego Garcia, more than 2,500 miles away in the Indian Ocean. B-2 stealth bombers made runs directly from Missouri. F/A-18 fighters flew hundreds of miles from aircraft carriers in the Arabian Sea.

To keep a "taxi rank" of aircraft in the skies, ready to fire weapons at a moment's notice, requires a phalanx of other assets: transport aircraft, air-to-air refuelling tankers, Awacs aircraft monitoring air traffic, reconnaissance aircraft, and - if the enemy has air defences - Prowler radar-jamming aircraft. Each aircraft carrier has its own battle group. The thousands of people involved have to be fed.

The Pentagon's expanded resources will be spent not just on refining the sharp end, with F-22 Raptor and F/ A-18 Hornet fighters, as well as the future F-35 Joint Strike Fighter. Much of the supporting infrastructure will also be renewed.

The Pentagon is negotiating with Boeing on a controversial plan to lease up to 100 new Boeing 767s as tanker aircraft. It is buying more Boeing C-17 and Lockheed Martin C-130J transport aircraft. The US Navy's ageing Prowler aircraft are urgently in need of replacement, with the F/A-18 the most likely candidate. Mr Rumsfeld has spoken often of stepping up building new ships to maintain naval strength.

US budget figures this week showed spending of $10.58bn over three years on 39 C-17s, and $1.7bn on 18 C-130Js - a total of $12.28bn. By contrast, eight European countries plan to spend $15.6bn, spread over more than 10 years, on 196 A400M transport aircraft. But the project is stalled because the German government cannot guarantee its share of the funding.

Kori Schake, a US defence expert who is about to join the National Security Council staff, says: "Few European armed forces have the capability to contribute substantially to high-intensity combat operations of the kind the US is carrying out; they lack the equipment and as a result operate very differently from US forces."

The gap can only widen. The Pentagon, with a research and development budget of $53.9bn for fiscal 2003, is spending over seven times more per soldier on next-generation technology than the whole European Union.

"European military forces are losing the ability to work in coalitions with US forces," she writes in a pamphlet published by the London-based Centre for European Reform.

Some US officials worry that the EU plan to develop a defence capability wastefully duplicates the Nato alliance without adding military punch. Officers stress the need for "interoperability" between allies - compatible equipment and doctrines that would make Nato forces seamless in combat. But the growing transatlantic disparity may render such arguments irrelevant, defence experts believe.

Ms Schake argues the EU should focus on equipment and technology that would improve on the tasks it can do, such as peacekeeping - even if this involved duplicating US assets. That would increase European military options in a crisis and make it less dependent on the US. "Americans must understand that reducing Europe's dependence doesn't reduce its desire to work with the US," she says.