From PBS.com:

In the first weeks after the statue of Saddam Hussein fell, a group of young American bureaucrats led by Ambassador L. Paul Bremer III set off to establish democracy in Iraq. "We had an ambitious goal," Bremer tells FRONTLINE, "to try to bring better government to Iraq and help them rebuild their economy [and] their country." One year later, as Bremer made a secret exit to evade insurgent attacks, the group left behind a thriving insurgency, economic collapse and much of its idealism. "Our grand initiative there [was] to bring democracy to Iraq," says Rajiv Chandrasekaran, former Baghdad bureau chief for The Washington Post. Instead, says Chandrasekaran, "we were leaving with our tail between our legs."

You can watch the program in it's entirety at PBS.com. If you want to know the truth behind what went wrong during the most crucial time period of the Iraq War and why, you must see this.