It's been said that, if 11th September 2001 was the day the world changed for America, then 20th March 2003 was the day America changed for the world.
Four leading voices of the BBC's coverage in the last five years, Jim Muir, Magdi Abdelhadi, Lyse Doucet and John Simpson give their varying assessments of how the Iraq invasion and subsequent insurgency developed.
They chart the missed opportunities and faulty assessments by the Coalition and the murderous exploitation of Iraq's post-war frailty by Saddam loyalists and foreign Islamists.
We also look at how the ripples begun in the Sunni triangle have since spread globally affecting the political and diplomatic balance worldwide.
In Programme Three, Lyse Doucet looks at how the Iraq War changed the regional balance of power.
How has Iran, an overwhelmingly Shi'ite nation, assumed a new role in Iraq, the Middle East and beyond in the last five years?
And, paradoxically, have American actions in the Middle East helped this ascent of Tehran and President Mahmoud Ahmadinejad?
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