What happened?

First it was going to be over in days, then the war looked like dragging on for months, then suddenly the end came. Or did it? Here Rupert Cornwell reveals what really went on.

Surely there has never been a war like it: so compressed, so minutely covered, short-lived by the standards of past wars, but seeming to last an eternity. Finally, however, with Saddam Hussein gone, American and British troops are wrapping up a job which, in truth, started 12 years ago.

Some talk of a historical triumph that will unlock a new and happier era for the entire Middle East. Others tremble at the prospect of exactly the reverse. But some survey the smouldering battlefield and wonder if somehow, despite the overthrow of a tyrant and all the destruction, we are not pretty much where we were before the shooting started.

Only two things may be said with certainty of this Gulf War II: that it is a pivotal moment in the way this planet organises, or disorganises, its affairs – and that never in the field of human conflict have so many talked so much nonsense in so short a time.

"Let the words I utter today be sweet and tasty, for I may have to eat them tomorrow," Mo Udall, the late Arizona congressman and celebrated wit, once observed. Over the past three and a half weeks, positive banquets of false predictions have been force-fed back to their authors.

When the war opened with that strike in the early hours of 20 March on the "target of opportunity" in southern Baghdad, we even hoped for an instant that it might be over before it had begun, with a precision strike that had killed Saddam and his closest henchmen at one fell swoop. The next day American armour, carrying its complement of "embedded" correspondents super-charged with adrenalin, raced across the desert as the serious bombing of "regime targets" in Baghdad got under way. The fighting had started and, with not an enemy to be seen, would surely be over before the reporters got their shirts dirty. Those who feared a protracted and bloody conflict went silent. But not for long.

All of a sudden, things seemed to stall. The city of Basra and the port of Umm Qasr were assumed to be pushovers; instead they put up stubborn resistance. As the 3rd Infantry Division and the US Marines 1st Expeditionary Corps swept north, the experts warned about overextended supply lines. Guerrilla raids and suicide attacks multiplied; who were these "Fedayeen" whom no pundit had ever mentioned? Stand up everyone who thought it would be a cakewalk.

At that point, inevitably, you started to notice the V-word. The US was being sucked into another Vietnam, some said – even though that war lasted 10 years, and this one hadn't even been in progress for 10 days. Such are the distortions of 24-hour television news coverage, and the perils attendant in a country accustomed to instant satisfaction. But not only armchair generals complained; real ones did too. "This enemy wasn't the one we wargamed against," noted Lieutenant General William Wallace, the commander of US ground forces in Iraq.

Even Donald Rumsfeld's jutting jaw seemed to sag a little, though the Pentagon continued to insist that everything was on track, and that the war plan was "brilliant". And in a few days it once again appeared precisely that. The advancing columns found a second wind and brushed aside vaunted Republican Guard divisions to reach the gates of Baghdad. Nor did they hang around on the doorstep. In the space of 48 hours, "sustained reconnaissance" missions metamorphosed into the capture of the city. Less than three weeks after President Bush declared "Let's Go!" in the White House situation room, Saddam Hussein's bronze statue was hauled from its pedestal in Firdos Square. His regime was gone – and the doubters slunk back into their lairs.

"We Must Not Gloat" was the watchword in official Washington. But the White House was ebullient, and Rumsfeld of Arabia consigned Saddam along with Stalin, Hitler and Ceaucescu into the litter bin of "failed dictators". And what of those doomsayers who predicted that in its death throes, the regime would attack Israel, launch chemical and biological weapons against the troops, and torch the Iraqi oilfields? "Just plain wrong," as the Secretary of Defence might put it.

Euphoria, however, lasted all of 24 hours. By Friday, looting was sweeping Baghdad and other major Iraqi cities, in an anarchy which seemed to take those masterful military planners in the Pentagon completely by surprise. As mobs rampaged through the capital, and a returning cleric on whom many hopes of national reconciliation rested was murdered in the holy city of Najaf, talk of smooth passage to an ordered, democratic and peaceful Iraq seemed ludicrous. Jay Garner, the man supposed to run the so-called Interim Iraqi Authority, by Friday had ventured no further than Umm Qasr.

That afternoon Rumsfeld, in particularly ebullient fettle, tried to make light of the problems: temporary chaos in the wake of such upheaval was only to be expected, "but more of our people coming into the country every day", he assured at a Pentagon briefing, before grinning, "Are we in a quagmire?" Maybe not, but it sure looks like it. In a few days, however, the rioting might have subsided; General Garner might be firmly in the saddle – and the doubters will again be forced into retreat.

There rests this not-quite-won war. At the time of writing the vice is tightening around Saddam's family stronghold of Tikrit. The dictator's exact fate is unknown, and no weapons of mass destruction have yet been found – even though they were ostensibly the reason the invasion was launched. But the most obvious lesson of the past three weeks has been hammered home around the world: where modern warfare is concerned, the US is in a class of its own.

Not that Iraq provided much opposition. After 12 years of sanctions, intermittent United Nations inspections and a quiet but sapping air campaign waged by Britain and the US in the no-fly zones, its forces were far weaker than in 1991. America, however, is far stronger than it was then, especially in the more important field of technology. Whereas barely 10 per cent of its munitions were precision guided in Gulf War One, this time only 10 per cent were not. Electronic command and control had made giant strides, giving US commanders the capacity to strike with unimaginable speed.

The most stunning example was last Monday's attack on a villa in the Mansour district of Baghdad, which some think killed Saddam Hussein. US intelligence received word that the Iraqi leader might be there and a B-1B bomber patrolling hundreds of miles from the capital was alerted. The aircraft changed course; the co-ordinates of the target were fed into its computers, and just 45 minutes after the initial alert two 2,000lb "bunker buster" bombs speared into the complex and exploded. This was warfare as never before practised, in which the desire could become the deed almost instantaneously.

"Shock and awe" was how the Pentagon dubbed the heavy bombing of Baghdad, the shuddering, multicoloured explosions that billowed nightly on our television screens. But viewers never saw images of what was arguably the most pulverising and deadliest use of American power, as air and ground forces linked, transferring in a split-second battlefield data to destroy Republican Guard tanks and units, often even before they realised they were under threat.

American forces moved with a speed that kept Iraqi defenders permanently off balance. Rumsfeld's concept of a "rolling invasion" – that victory could be secured by a relatively small number of highly trained troops, working closely with US air power and special forces, with reinforcements arriving later – has been vindicated. This conflict has already set a benchmark for 21st-century warfare, giving the lie to the old maxim that an invading force had to outnumber defenders by a ratio of three to one to cancel out the latter's inbuilt advantages. Technological superiority (aided, it should be said, by the ineptitude and bewilderment of the Iraqis) put paid to that. The result was a military mismatch for the ages, the equivalent of sending Lennox Lewis to sort out a school bully.

However, to reach into the trusty arsenal of Churchillisms, the conclusion of this war will not be the end of Iraq's agony, nor even the beginning of the end, but merely the end of the beginning. Fine troops with the best equipment and the most devastating firepower will guarantee the US victory in any fight. But they cannot make the peace. "War lite" might have been devastatingly effective but it left the coalition without enough forces to maintain order.

The truths which existed when the first American and British troops went in exist today. Iraq was, is and will be a desperately difficult country to remake, in an extraordinarily unstable region. Nor does military victory hide the fact that the UN, transatlantic relations and perhaps global stability have been dealt terrible blows by the Iraqi crisis. Washington must now show qualities the Bush administration is normally pretty short on: patience and magnanimity.

American treasure alone will not remake Iraq. It will take time – lots of it – constant attention, and a sensitivity that comes only from serious study of the problem at hand. James Dobbins, a former senior US diplomat with experience of Kosovo, Bosnia and Afghanistan, is blunt. "I've never seen a nation-building operation of this kind which takes place in less than five years." And that is probably over-optimistic.

The initial omens are not good. Having spurned Washington by denying its bases, Turkey has served notice it will tolerate no attempt by the Iraqi Kurds to create their own state. And anyone who believes the creation of a stable government will be the proverbial cakewalk should consider the murder of two Shia clerics at the Imam Ali Mosque in Najaf, and the political uproar when the British unveiled a "sheik" designated to take a semblance of charge in Basra (not least because he was a former brigadier general in President Saddam's army).

Many of us who opposed the war did so not out of any fondness for the Iraqi leader nor even the belief that the threat posed by his weapons of mass destruction was absurdly overblown. We did so because we believed the risks to regional stability outweighed the potential gains. Nothing so far has changed that judgement; indeed Turkey's behaviour, the current chaos in Iraq and the American sabre-rattling against Syria only confirm it.

And while the war has come and almost gone, the shambles of what is optimistically called the "international community" persist. Can the UN regain a semblance of authority, after the paralysing divisions on the Security Council before the conflict? Will those divisions spill over into trade wars and financial quarrels, complicating global economic recovery? Can the EU heal its wounds? Can the US on the one hand, and France, Germany and Russia on the other, mend fences – or will Gulliver say "to hell with it", less inclined than ever to permit the Lilliputians to tie him down in treaties and multilateral organisations?

Reconciliation is a two-way street. Ultimately it all depends on how America chooses to conduct itself. Among the journalists who were victims of the war was Michael Kelly, an outstanding columnist and writer, killed when the military vehicle in which he was travelling came under attack in central Iraq. But it is more than simple homage to a colleague to quote the closing lines of his final column in the Atlantic Monthly magazine, published after he died.

The real question, Kelly argued, is "whether the employment of [America's] almost unfathomable power will be largely for good, leading to the liberation of a tyrannised people and the spread of freedom; or largely for bad, leading to a corruption of America's own values and freedoms. Probably the next hundred years hinges on the answer." That is no exaggeration. It was true before the war, and is still truer today. The past 25 days have changed everything, in the Middle East and beyond. Yet, in a deeper sense, they have changed nothing.