Doctor Mohammed Ali would be the perfect candidate to be an ardent supporter of America's war in Iraq.

A secular Shia professional who chafed under the repression of Saddam Hussein's regime, he was overcome with joy when American troops entered Baghdad four years ago this Sunday. "I was screaming, rejoicing in happiness," he told me during a recent trip to Baghdad. "The tyranny has ended."

Instead, a new kind of tyranny of fear began for him and his country as Iraq slipped into the abyss of a violent Sunni insurgency against the Americans and a bloody civil war between Sunni and Shia militias.

Lose Baghdad, you lose Iraq. Lose the people and you lose the war. And America is in danger of losing Baghdad and its people.

For Dr. Ali, it began to crumble in the months after the occupation, when basic services such as water, electricity – not to mention medical supplies – could not be guaranteed.

The doctor – who asked that his real name not be used -- tried to stay above the fray, treating the mounting casualties of war – until he and his colleagues became the casualties. The militias began singling out doctors, nurses and other professionals for assassinations. "They wanted to turn the life into a hell,' he said. "They targeted the scholars, physicians, the specialists."

He personally knows of more than hundred doctors who have been killed. Just before Dr. Ali was to be certified as a specialist after five years of study, the lead examiner was killed and the others fled – forcing Dr. Ali into hiding for fear of his life.

The terror – from all sides – reaches into the highest corridors of power. I met with Tariq Al-Hashemi, one of Iraq's two vice-presidents and the country's leading Sunni politician. In the past year, he has buried two brothers and a sister, killed by Shia death squads.

One of the moderate Sunni leaders courted by President George Bush –- who received Hashemi in the White House – the vice president remains remarkably optimistic. "I have no choice (but to) leave my person grief aside and go forward to shake hands with others to rebuild my country," he said.

But, ominously, our interview at his heavily fortified compound was interrupted by loud yelling in the office next door. One of his staff members, the vice president told me, was negotiating on the phone with kidnappers who had recently seized his son. And in a twist of terror that says much about how deep Iraq has sunk into the chaos of a splintering war the kidnappers were Sunnis, not Shias.

The American troops on the ground realize that time is running out for them to secure the capital and its people.

I rode in Humvees with a small team of American soldiers working with Iraqi security forces to drive the militias out of Rustamayah, a neighbourhood in eastern Baghdad. They were looking for help from the people.

"It's really a race," said Major Rob Goodroe. "Can we get the information out of the public, or can the insurgents use their intimidation to keep the public quiet. Whoever wins that battle with the public is going to ultimately win the insurgency."

But – leaving aside whether one thinks the invasion was justified to begin with – it is a race which the American troops were perhaps doomed to lose from the start. The White House and its imilitary leaders ignored the Sunni-Shiite divide, the burgeoning insurgency and the perils of becoming an occupation force.

"We went to war with a failed strategy," said John Batiste, the former commander of the 1st infantry Division who quit the army to become one of the first generals to publicly criticize former Secretary of defense Donald Rumsfeld and his advisors. "They completely ignored the hard work to build the peace."

Now there is little peace to keep.

Dr. Ali remains a prisoner in his apartment, trapped by a war whose victims he cannot help. "I always hope that it is a big nightmare, that I will open my eyes in the morning and all this blood that has been shed, everything has never happened."

By coincidence, Dr. Ali's hideout was close enough to a suicide bomb attack near a university a few weeks ago that the windows on his apartment shattered.

"There were bodies all around," he remembered. "Cell phones are ringing, scattered, you cannot know what to do. You have to pick up the phone. What can you say? ‘Your son or your daughter is burning?'"

Julian Sher is the writer and director of Battle for Baghdad: No Way Out. This commentary was originally prepared for the Toronto Globe and Mail.