Rivalry with Iran was the main fuel of Saddam Hussein's quest for weapons of mass destruction, says a report from the Iraq Survey Group.
Much of the report was based on "debriefings" of Saddam and Baathist officials
The group, which found no stockpiles of banned weapons in Iraq, concluded that the former leader ultimately wanted to recreate his weapons capability.
The report bases many of its findings on US "debriefing" sessions with Saddam Hussein and former regime officials.
These also reveal new details about the former Iraqi leader's rule.
WMD were "an integral element in the range of tools Saddam drew upon to advance his ambitions", states the ISG report.
Weapons inspections had achieved their aim, it adds - Iraq had no WMD.
But Saddam Hussein was keen to preserve at least the appearance of a threat primarily as a deterrent to "Iraq's abiding enemy", Iran - "especially as it became obvious that Iran was producing the very capabilities he was denied".
His rivalry with Iran, the report says, was bound up with his own narcissism - "a sense of the longstanding rivalry over the centuries and his own desire to be seen as an historic military leader".
He believed that during the 1980-88 Iran-Iraq war, chemical weapon and ballistic missile attacks "had broken [Tehran's] political will".
He also believed his regime's chemical and biological weapons had prompted the US-led coalition to leave his regime in power during the 1991 Gulf War.
The former Iraqi president also valued science and technology highly, and viewed nuclear programmes as a "symbol of a modern nation, indicative of technological progress".
This, the report says, explains Saddam Hussein's wish to preserve the intellectual capacity to recreate weapons programmes.
'No explicit strategy'
But the report also says there are few indications of a concrete programme to renew Iraq's WMD capabilities behind the threat it projected.
"While he may have said he had the desire, no source has claimed that Saddam had an explicit strategy or programme for the development or use of WMD during the sanctions period," says the report.
His overriding ambition was to see sanctions dismantled, says the report.
Saddam Hussein was arrested in December 2003 in Iraq, in a hole in the ground near his hometown of Tikrit.
The report again identifies his desire to secure a place in history and "shape his legacy" - and not an eagerness to appease - as his reason for talking to his captors.
In another example of Saddam Hussein's regard for history, the report says bricks used during the reconstruction of the ancient city of Babylon were moulded with his name, in an attempt to make sure he would be remembered down the centuries.