Several stars have used the 2003 Oscar film award ceremony as a platform to voice their opposition to the war.
Due to the Gulf situation, the Oscars had been toned down with tight security and scaled-down red carpet entrances.
The musical Chicago won six prizes including Best Picture.
Roman Polanski was named Best Director for The Pianist.
A number of stars - including Daniel Day Lewis - wore peace emblems in protest against the war on Iraq.
As actress Susan Sarandon stepped up to make a presentation, she made a peace sign, but the biggest and loudest protest came from Michael Moore after he accepted the Best Documentary Oscar for Bowling for Columbine.
He said: "we live in a time where we have fictional election results that elect a fictional president".
His speech was greeted with boos and cheering from the star-studded audience.
Moore ended by saying: "We are against this war. Shame on you, Mr Bush".
Honorary Irishman Daniel Day Lewis, nominated for Best Actor in Gangs of New York, lost out to Adrien Brody in The Pianist.
U2, in the running for Best Original Song for Gangs of New York, were beaten by Eminem in 8 Mile.
Nicole Kidman won Best Actress for her role as Virginia Wolfe in The Hours and made a tearful acceptance speech.
The Best Supporting Actor Oscar went to Chris Cooper for Adaptation, while the award for Best Supporting Actress went to heavily-pregnant Catherine Zeta-Jones for her performance in Chicago.
Connemara-born Peter O'Toole was awarded an honorary Oscar for a 40-year career who said: "Always a bridesmaid never a bride, my foot - I now have my own Oscar now until death do us part."
