We are on the brink of war in Iraq. It was always going to be this way. President George W Bush probably knew on the 12 September 2001 that his country's forces would be attacking Baghdad at some point in the next few years. Just as it was decided within hours of the horrendous events of the day before that Afghanistan's Taleban regime, one of the world's poorest and least capable of defending itself, would soon face the awesome might of the US military.

Afghanistan was an obvious soft target to temper the wrath of a profoundly shocked and fearful American people. The use of Afghan soil to train many of those whose hate fuelled the World Trade centre attacks was a prima facie reason to force regime change in Kabul. It was done, although only in the broadest, most brutal sense. What's fallen between the cracks are the subtleties of manipulating post-Taleban Afghan politics to rule out more 9/11's. Gunboat diplomacy by great imperial powers rarely produces lasting, satisfactory results. Hamid Karzai reigns but does not rule in his own country: the parched hills and defiles of the borderlands, so well known to Karzai from his years as a fighter against Soviet imperialism, are still a breeding ground for venom and fury that will soon be directed outward.

Which brings us to Iraq. Saddam Hussein played his cards well from his own twisted point of view. And at the table with him were far wealthier, far more powerful players. George Bush Sr and Margaret Thatcher, the architects of the first Western war against him, both fell to the forces of democracy, which failed to unseat Saddam. He outlasted John Major and Bill Clinton too. When the latest Bush slipped mysteriously into office in the United States, Saddam joked that "he'd seen off the father, now he would survive the son too." Britain's Tony Blair-a more legitimate elected leader than George W Bush-won two elections while the bloodstained dictator of Baghdad mocked American and British might by remaining in power, despite countless sorties and bombing raids against Iraqi targets in the southern and northern "no fly zones". No one seemed to care in the US or the UK.

But on 12 September 2001, Iraq appeared on a list of targets that America just had to hit. Never mind that the situation had festered for years, that George Bush Sr and John Major had lost their nerve in 1991, the last best chance for getting rid of the Butcher of Baghdad. Now, a full decade later, it was time. It is time for war. For days and weeks of high-tech videogame displays of smart munitions crashing home in fuzzy black and white screen television pictures, "bombs-eye-view" graphic displays, gruff manly press briefings by ministers, secretaries and generals. One-sided, jargon-laden analysis by retired officials with similar pedigrees. Troubled reportage by a few brave souls, but most American journalists getting metaphorically into uniform and cheering on the sidelines. It is time for death on both side, brave soldiers and civilians, cowards and heroes, rich and poor, privileged and backward.

Public opinion is uncertain at best, uneasy with the political preparations or unaware of the medium and long-term implications. And that's just America. In Britain, France, Germany, Australia, Canada, New Zealand, Italy, Spain and just about every Asian, African and Latin American country, the majority don't want war. With their massive protests of recent days, they've proved that. But leaders of those countries are privy to more complex information. They know that America's wrath will fall on those who don't help in Iraq. So they support the White House and pray for violence to end quickly. It might. But what comes next is most interesting. And how America continues to behave as the real battle rages.

That battle is not for Iraq, Afghanistan or even to wipe out the evil men of al-Qaeda. That's for the heart and soul of the US and its standing in the world. Imperial power is squaring off against liberal conscience, boardroom heroes basking in the glory of a brave military are taking on those who truly believe in the values of the American republic, and interpret them as fairness, decency, justice and generosity.

Watch that battle closely. It's the one that matters most.