The US attacked Iraq in 2003 based on either misformation or disinformation, and the stated reasons have changed over time.
The Initial Justification : Weapons of Mass Destruction
The primary reason given by the administration of George W. Bush was that Saddam Hussein, the leader of Iraq, was engaged in the production or acquisition of weapons of mass destruction (WMDs). These are nuclear, chemical, or biological weapons (examples are the anthrax letter attacks in the US and the Sarin gas attacks in Tokyo--neither of which had any connection to Iraq). It was suggested that Hussein might provide these weapons to terrorists to attack the US. He had already used chemical weapons sold to him by the US against Iran, and also against Iraqi Kurds. Before the war UN inspectors announced they had found no evidence of WMDs, despite unfettered access. After the war was under way, additional investigation concluded Saddam did not have WMDs.
The war continued, however, because the occupation forces of the US were attacked by Iraqi guerrillas, many ironically supported by Iran, Iraq's enemy in the Iran-Iraq war (1980-1988). The US supported a new democratic government within Iraq, which was opposed by various Islamic groups that traditionally held power in the country. Other factions sought to aggrandize their share of the power to be had in the new political system.
It was suggested early on the conflict was predominantly an attempt by the US to control the flow of oil from Iraq, one of the largest petroleum producers in the Middle East.
Secondary Justification: Fostering a Democracy in Iraq
Initially when the US commenced Operation Iraqi Freedom in 2003, it was a war against the regime in Iraq; to remove Saddam from power, as the US had failed to do in 1991. The goal of the 1991 operation was to drive Saddam from Kuwait, at which the US and its allies succeeded. When no WMDs were found, the US asserted that its mission in Iraq was two-fold: to create a modern democracy and to stop the persistent genocides that took place in that country. The US enfranchised the Shiite Majority, provided for Kurdish autonomy in the North, and assembled a Constitution for the entire Iraqi population. This is in stark contrast to Saddam Hussein who used chemical weapons on his own population and was responsible for committing genocide against the Shiite Arabs, Marsh Arabs, Kurds, Jews, Azeri, Assyrians, Yazidi, Bahai'i, and Chaldeans among others.
The Bush administration believed that Iraq had Weapons of Mass Destruction
The United States eliminated Iraq's dictator but created resentment among many Muslims.
The United States eliminated Iraq's dictator but created resentment among many Muslims.
Since the overthrow of Saddam Hussein (2003) and the US occupation there (2003-2011), Iraq is considered an ally of the United States and continues to receive military and foreign aid. The neighboring country of Iran, which has supplied guerrillas and other factions fighting the US, is considered (unofficially) an enemy of the United States.
To remove "Weapons of Mass Destruction" from Saddam's control. It's worth noting that the phrasing in the question of "its allies" is incorrect. Iraq was not invaded in 2003 by any country that it would have considered its allies. The United States was seen as an enemy imperialist power in Iraqi political circles as was the United Kingdom.
United States military invasion of Iraq took place at dawn on March 20, 2003.
The United States removed Iraq's oppressive dictator.
The Iraq War begin on March 19 2003 when United States troops invaded Iraq. This was called Operation Iraqi Freedom by the United States.
In both the first(1990-1991) and the second(2003-present) the United States fought against Iraq.
The Iraq War between Iraq and the United States began on March 20th, 2003. It wasn't until December 2011 that the United States started to pull troops.
The United States supported its fight against Iran. They were trade partners. The United States sold Iraq a huge arsenal of weapons. The United States supported its fight against Iran.
Many countries fought in Desert Storm. The most important, arguably, were the United States and Iraq.
The Bush administration believed that Iraq had Weapons of Mass Destruction
The 2003 invasion of Iraq, (from March 20 to May 1, 2003) was led by the United States, alongside the United Kingdom and smaller contingents from Australia, Denmark and Poland.
The United States suppported the fight against IranThe United States sold Iraq a huge arsenal of weapons.
The United States suppported the fight against IranThe United States sold Iraq a huge arsenal of weapons.
The entire campaign of the United States against Iraq under Bush II smacked of jingoism.