Ali Abd al-Amir Allawi, who was appointed on Sunday to lead the defence ministry, is currently serving as the war-torn country's interim trade minister.
Muhammad Abd Allah Muhammad al-Shahwani, a former military officer who was forced into exile, was named the director general of the new national intelligence service.
US occupation administrator Paul Bremer announced the establishment of a new defence ministry and intelligence service to, he said, defend the country against "terrorists and insurgents".
Before becoming the interim trade minister, Allawi, who was born in 1947, was a senior assistant at the Centre of Middle Eastern Studies of St Anthony's College, at Oxford University in Britain.
He earned a bachelor of science degree in civil engineering from the Massachusetts Institute of Technology in 1968 and a masters in business administration from Harvard in 1971.
A staunch opponent of Saddam's ruling Baath party since the late 1960s, Allawi also managed several investment organisations before joining Iraq's post-war leadership.
Shahwani, also born in 1947 in the northern Iraqi city of Mosul, was a major-general in Saddam's disbanded army who was forced into retirement in 1984 by the Revolutionary Command Council.
He lived under surveillance until 1990 when he managed to flee Iraq for Britain, where he led an underground movement opposed to the regime until 1996.
Saddam discovered the organisation and his henchmen assassinated several of its members, including three of Shahwani's sons.
Shahwani also fought in US-led ranks to oust Saddam's regime in the 2003 war.
The US-led occupation force dismantled the Iraqi army and the powerful intelligence services last May, a month after toppling Saddam's regime.