Kenneth Branagh will star in one of a series of hard-hitting short BBC films based on the invasion of Iraq in 2003.
Branagh will play Colonel Tim Collins of the Royal Irish Regiment
He will appear in the last episode of 10 Days To War, which tells the story of the build-up to military action.
Branagh plays Colonel Tim Collins, whose speech to British soldiers hours before they went into battle in Iraq made headlines around the world.
The drama follows the Royal Irish Regiment officer as he prepares to cross the border into Iraq.
The films were an "original way of exploring one of the most controversial moments in recent history," BBC Two controller Roly Keating said.
The 10-minute films will air next month on BBC Two.
Meanwhile, former ER star Alex Kingston will join Doctor Who for two episodes, the BBC has also announced.
She will play River Song, a mysterious character who meets the Doctor on an expedition to uncover the secrets of an abandoned library.
"I'm so delighted to be a part of the new series," she said.
"I used to watch Doctor Who through the crack in the door. I was so terrified but I couldn't tear myself away."
The fourth series of Doctor Who is currently being filmed in Cardiff and will be broadcast on BBC One in the spring.