Baghdad ? In the beginning, it all looked simple: topple Saddam Hussein, destroy his purported weapons of mass destruction and lay the foundation for a pro-Western government in the heart of the Arab world.

Nearly 4,500 American and more than 100,000 Iraqi lives later, the objective now is simply to get out — and leave behind a country where democracy has at least a chance, where Iran does not dominate and where conditions may not be good but “good enough.”

Even those modest goals may prove too ambitious after American forces leave and Iraq begins to chart its own course. How the Iraqis fare in the coming years will determine how history judges a war that became among the most politically contentious in American history.

Toppling Saddam was the easy part. Television images from the days following the March 20, 2003, start of the war made the conflict look relatively painless, like a certain type of Hollywood movie: American tanks speeding across the bleak and featureless Iraqi plains, huge blasts rattling Baghdad in the “shock and awe” bombing and the statue of the dictator tumbling down from his pedestal.

But Americans soon collided with the complex realities of an alien society few of them knew or understood. Who were the real power brokers? This ayatollah or that Sunni chief? What were the right buttons to push? America had its own ideas of the new Iraq. Did most Iraqis share them?

Places most Americans had never heard of in 2002, like Fallujah and Abu Ghraib, became household words. Saddam was captured nine months after the invasion. The war dragged on for eight more years. No WMD were ever found. And Iraq drained billions from America’s treasury and diverted resources from Afghanistan, where the Taliban and al-Qaida rebounded after their defeat in the 2001 invasion.

In the early months, America’s enemy was mostly Sunnis angry over the loss of power and prestige when their patron Saddam fell. In September 2007, the bloodiest year for U.S. troops, Shiite militias — part of a community that suffered terribly under Saddam — were responsible for three-quarters of the attacks in the Baghdad area that killed or wounded Americans, according to the then-No. 2 U.S. commander in Iraq, Lt. Gen. Ray Odierno.

Saddam had not tolerated al-Qaida. With Saddam gone and the country in chaos, al-Qaida in Iraq became the terror movement’s largest and most dangerous franchise, drawing in fighters from North Africa to Asia for a war that lingers on through suicide bombings and assassinations, albeit at a lower intensity.

As American troops prepare to go home by Dec. 31, they leave behind a country still facing violence, with closer ties to the U.S. than Saddam had but still short of what Washington once envisioned. Iranian influence is on the rise. One of the few positive developments from the American viewpoint — a democratic toehold — is far from secure.

Boiling over

In 20-20 hindsight, the U.S. probably should have seen it coming. By 2003, communal rivalries and hatreds, fueled by years of Saddam’s suppression of Kurds and Shiites, were brewing beneath the lid of a closed society cobbled together from the wreckage of the Ottoman Empire after World War I. Saddam’s rule of terror kept all these passions in the pot. Lift the lid and the pot boils over. Remove Saddam and a new fight flares for the power that the ousted ruler and his Baath Party had monopolized for decades.

A day after Saddam’s statue was hauled down in Baghdad, the U.S. arranged what was supposed to be a reconciliation meeting in the Shiite holy city of Najaf, bringing together prominent clerics from the majority Shiite sect eager for a dominant role in Iraq after the collapse of Saddam’s Sunni-dominated rule.

One of them was Abdul-Majid al-Khoie, son of a revered ayatollah. Al-Khoie had fled to Britain during Saddam’s crackdown against Shiites after the 1991 Gulf War. Now he and the other clerics were back in Iraq, freed from Saddam’s yoke.

As al-Khoie approached a mosque, a crowd swarmed around him. He was hacked to death in an attack widely blamed on Muqtada al-Sadr, a fellow Shiite cleric.

In Baghdad, meanwhile, mobs looted and burned much of the city as bewildered U.S. soldiers stood by.

“Stuff happens,” then-U.S. Defense Secretary Donald H. Rumsfeld famously said at the time. “And it’s untidy, and freedom’s untidy, and free people are free to make mistakes, and commit crimes and do bad things. They’re also free to live their lives and do wonderful things. And that’s what’s going to happen here.”

Within months, angry Sunnis had taken up arms to resist what they saw as a Shiite takeover on the coattails of the Americans. Their ranks were bolstered by former soldiers whose livelihood was taken away when the Americans, in a bid to appease Shiite and Kurdish leaders, abolished Saddam’s military.

America was in for a long and brutal fight. The triumphant scene of Saddam’s statue falling would be replaced by new iconic images: the bodies of butchered Americans hanging from a bridge in Fallujah, military vehicles engulfed in flames, terrified hostages staring into a video camera moments before decapitation, and flag-draped caskets resting at open graves as aging parents and young widows wept for their loved ones.

Ideals clash

The Americans arrived with their own agenda for the new Iraq. That didn’t always mesh with what the Iraqis had in mind.

Phillip J. Dermer, a now-retired U.S. colonel who has returned to Iraq as a businessman, spent the summer of 2003 helping set up a city council in Baghdad.

The idea was to give Iraqis a quick taste of democracy while issues like a constitution and national elections were being worked out.

After months of preparation, the council was elected and got down to its first order of business: To the Americans’ surprise, an al-Sadr representative came forward to change the name of the Shiite slum in eastern Baghdad from Saddam City to Sadr City in honor of the cleric’s father, who was assassinated by the deposed regime. The measure passed unanimously.

Dermer and his colleagues had been expecting a vote for something like a new budget for water. For Dermer it was a signal. The Iraqis had their own priorities.

The Americans would soon learn the Iraqis were primarily interested in promoting their own religious or ethnic group at the expense of others.

Civil war

Increasingly, Sunni militants were targeting not just U.S. troops but Iraqi Shiites.

Shiites initially held their fire and did not retaliate. Their highest-ranking cleric, Grand Ayatollah Ali al-Sistani, wanted Shiites to keep focused on the main prize: majority control of the government.

All that changed with the bombing of a major Shiite shrine in Samarra in February 2006.

Newly formed Shiite militias struck back against random Sunnis, often dragging them away in the dead of night. It was now Shiites against Sunnis, neighbor against neighbor.

America was now in the middle of a civil war, partly of its own making, despite intense efforts by the Bush administration to resist that view.

In January 2007, President George W. Bush announced he was sending 30,000 more troops to secure Baghdad and the provinces around it. Talk of a troop withdrawal in 2007, which had been widely expected, disappeared. With the Americans promising and paying for support, more and more Sunni insurgents switched sides and turned against al-Qaida. Eight months into the surge, Shiite militia leader al-Sadr declared a cease-fire and violence began dropping in the capital.

Fighting continued. But the commanding general, David Petraeus, was able to tell Congress by the end of the year that the “military objectives” of the surge were being met.

Conflict continues

By New Year’s Day 2012, America’s role in the Iraq war will be over. For Iraqis, however, the war and the struggle to build a functioning democratic state continue. Bombs still explode, gunmen attack police checkpoints. Iraq’s government, though far more representative than Saddam’s regime, still falls short of an ideal.

Tensions between Sunnis and Shiites, Arabs and Kurds remain unresolved. It’s an open question who will ultimately govern in Iraq and whether Iran will in time come to dominate its weakened neighbor.

America will not be abandoning Iraq. The U.S. will leave behind thousands of diplomats and security contractors, whose presence will influence the direction of the country for years to come. Still, the disappearance of uniformed troops will have a profound effect on Iraqis in ways that will take years to define.

For the first time in nearly nine years, Iraq’s future will be entirely in the hands of Iraqis.