Northern Iraq, or what Kurds call Kurdistan, is home to a potentially volatile mix of Kurdish, Arab, and Turkoman populations in cities such as Mosul, Erbil, and Kirkuk. Some fear that tensions between Kurds and Arabs in strategic, oil-rich Kirkuk could lead to civil war. Others see hope for stability and prosperity under a new, democratic Iraqi government -- as long as the U.S. doesn't pull out too soon. Addressing the situation in northern Iraq, in excerpts from FRONTLINE's interviews, are General David Petraeus in Mosul, Colonel William Mayville in Kirkuk, and PUK leader Barham Saleh in Suleimaniya.

The area of central Iraq known as the Sunni Triangle, to the west and north of Baghdad, has been the focal point of violent resistance to the U.S.-led occupation. Long dominated by powerful Sunni Arab tribes and Saddam Hussein's Baathist regime, many Sunnis now fear retribution by the majority Shiites and marginalization in a democratic Iraq. Here are excerpts from FRONTLINE's interviews with Col. William Mayville, tribal leader Sheikh Gazi al-Essawi, and Maj. Gen. Raymond Odierno.

Iraq's long-oppressed Shia majority, who dominate the southern half of the country, stand to take a leading role in a new, democratic Iraq. This worries many of their fellow Iraqis, and some in Washington, who fear an Islamic state aligned with neighboring Iran. But Iraq's Shiites are not a monolithic bloc -- they, too, are divided between radical and moderate, Islamist and secular. Here, discussing these issues in excerpts from FRONTLINE's interviews, are The New Yorker's Jon Lee Anderson, Iraqi Governing Council members Abdul Aziz al-Hakim and Adnan Pachachi, and Grand Ayatollah Mohammed Taqi al-Modarresi.

Political and social reality in Iraq, like any country, is far from simple. No one knows this better than the American military commanders who have been based in places like Mosul, Kirkuk, and Tikrit, and who have been handed the job of not only fighting a tenacious guerrilla insurgency but also sorting out the complex and potentially explosive relations between Iraq's ethnic and sectarian groups. Here are excerpts from FRONTLINE's interviews with Maj. Gen. Raymond Odierno in Tikrit; Col. William Mayville in Kirkuk; and Maj. Gen. David Petraeus in Mosul.