Thomas Friedman / The New York Times

Iraq might seem to have been the last place in the Middle East we should have tried to help establish a democracy, but it was the most important.

On this 10th anniversary of the U.S. invasion of Iraq, three things are clear. First, whatever happens in Iraq, we overpaid for it in lives and treasure and focus. Second, you can overpay for something decent and you can overpay for total junk. What exactly we overpaid for in Iraq is not yet clear and will be decided by Iraqis. Third, as much as we'd prefer to forget about Iraq, what happens there matters more than ever for the Middle East.

Given its history of brutal dictatorship, Iraq might seem to be the last place in the Middle East we should have tried to help give birth to a self-governing democracy. In fact, it was the most important. Just look at Syria and you'll understand why. Iraq was made up of all the sects that populate the different Arab countries and have been held together over the last 50 years by iron-fisted dictators. If Iraqis could demonstrate that, once their dictator was removed, the constituent communities of Iraq (Shiites, Sunnis, Kurds, Turkmen, Christians) could forge their own social contract for living together peacefully — rather than being ruled brutally from the top down — then some kind of democratic future was possible throughout the Arab world.

That possibility is yet to be fulfilled. We toppled the dictator in Iraq. The people have done the same in Tunisia, Egypt, Yemen, Libya and, soon, Syria, but the same questions hang over all of them: Can they produce stable, decent, representative governments? Can Shiites, Sunnis, Kurds, Christians — or secularists and Islamists — live together as citizens and share power? If so, democratic politics has a future in this region. If not, the future will be a Hobbesian nightmare, where the iron-fisted dictators are removed but are replaced by rival sects, gangs and tribes, making impossible the decent governance needed for human development for millions of Arabs.

Today there are no outsiders — no Ottomans, Europeans, Americans, Arab League or U.N. — who want to govern in the place of dictators and no dictators who can sustain their iron fists. So either the communities in these Arab states find a way to share power or the entire Arab world is going to become like one of those regions on medieval maps labeled: “Beware: Here Be Dragons.”

That is why the most important peace process in the Middle East today is the one needed between Sunnis, Shiites, Christians, Kurds, as well as Islamists and secularists. Despite our costly mistakes — and all of Iraq's neighbors and Sunni jihadists trying to make Iraq fail (see Tuesday's killings) — we eventually helped Iraqis write their own democratic Constitution to resolve their differences politically, if they want to. None of the other Arab transition states have either an external midwife or internal Nelson Mandela to do this. All are at the start of long, hard struggles.

Anyone interested in what is actually happening in Iraq today should read Roula Khalaf's lengthy 10th-anniversary piece in Saturday's Financial Times, which shows a country progressing and regressing at the same time. “Outside Baghdad University,” she wrote, “I sit in a minibus and chat with students. Alia, a 24-year-old studying for a master's degree in biology, says young people are enjoying access to the Internet, to the dozens of satellite channels that have been set up in Iraq, and adds that, despite the political struggle between the elite, there is no sense of division between Sunni and Shia at the university. Yet she too is dissatisfied, her family always worried about her whereabouts. ... 'Freedom is important, but it doesn't give me enough,' she says. 'Freedom should be about being able to do what you want, not just talk.'”

I believe the real agent of change in postauthoritarian societies is something that takes nine months and 21 years to develop. It's called “a new generation,” one that thinks and acts differently from its parents'. Any honest look at Iraq today reveals seeds of civil society sprouting and poisonous sectarianism spreading. I hope the 20th anniversary is an occasion for a more positive judgment.