The 2003 invasion of Iraq (March 19–May 1, 2003), was the start of the conflict known as the Iraq War, or Operation Iraqi Freedom, in which a combined force of troops from the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and Poland

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

 invaded Iraq and toppled the regime of Saddam Hussein

Saddam Hussein

Saddam Hussein Abd al-Majid al-Tikriti was the fifth President of Iraq, serving in this capacity from 16 July 1979 until 9 April 2003...

 in 21 days of major combat operations. The invasion phase consisted of a conventionally fought war which concluded with the capture of the Iraq capital Baghdad

Baghdad

Baghdad is the capital of Iraq, as well as the coterminous Baghdad Governorate. The population of Baghdad in 2011 is approximately 7,216,040...

 by United States forces.

Four countries participated with troops during the initial invasion phase, which lasted from March 19 to April 9, 2003.