Opposition to the Iraq War significantly occurred worldwide, both before and during the initial 2003 invasion of Iraq by a United States–led coalition, and throughout the subsequent occupation. Individuals and groups opposing the war include the governments of many nations which did not take part in the invasion, including both its land neighbors Canada and Mexico, its NATO allies in Europe such as France and Germany, as well as China and Indonesia in Asia, and significant sections of the populace in those that took part in the invasion."China condemns U.S. for Iraq war" . The Star (from Associated Press). March 7, 2007. Opposition to the war was also widespread domestically.

Rationales for opposition include the belief that the war is illegal according to the United Nations Charter, or would contribute to instability both within Iraq and the wider Middle East. Critics have also questioned the validity of the war's stated objectives, such as a supposed link between the country's Ba'athist government and the September 11 attacks on the United States, and its possession of weapons of mass destruction "certified" by the Niger uranium forgeries. The latter was claimed by the United States during the run-up to the war, but no such weapons were ever found.

Within the United States, popular opinion on the war has varied significantly with time. Although there was significant opposition to the idea in the months preceding the attack, polls taken during the invasion showed that a majority of US citizens supported their government's action. However, public opinion had shifted by 2004 to a majority believing that the invasion was a mistake, and has remained so since then. There has also been significant criticism of the war from US politicians such as Bernie Sanders, national security and military personnel, including generals such as Anthony Zinni and Paul Eaton who served in the war and have since spoken out against its handling, including calling for former Secretary of Defense's Donald Rumsfeld resignation. Lieutenant General Gregory S. Newbold, openly critical of Rumsfeld's plans for the invasion of Iraq, resigned in protest prior to the invasion.

Worldwide, the war and occupation have been officially condemned by 54 countries and the heads of many major religions. Popular anti-war feeling is strong in these and other countries, including the US' allies in the conflict, and many have experienced huge protests totalling millions of participants.

Early opposition The opposition to the war manifested itself most visibly in a series of worldwide protests against the Iraq War during February 2003, just before the invasion of Iraq starting on March 20, 2003. Noam Chomsky said:

Reasons for opposition

Critics of the invasion claimed that it would lead collateral damage to deaths of thousands of Iraqi civilians and soldiers as well as Coalition soldiers, and that it would moreover damage peace and stability throughout the region and the world.

Another oft-stated reason for opposition is the Westphalian concept that foreign governments should never possess a right to intervene in another sovereign nation's internal affairs (including terrorism or any other non-international affair). Giorgio Agamben, the Italian philosopher, has also offered a critique of the logic of preemptive war.

Others did accept a limited right for military intervention in foreign countries, but nevertheless opposed the invasion on the basis that it was conducted without United Nations' approval and was hence a violation of international law. According to this position, adherence by the United States and the other great powers to the UN Charter and to other international treaties is a legal obligation; exercising military power in violation of the UN Charter undermines the rule of law and is illegal vigilantism on an international scale.

There was also skepticism of U.S. claims that Iraq's secular government had any links to Al-Qaeda, the Islamic fundamentalist terrorist group considered responsible for the September 11 attacks on the World Trade Center and Pentagon.Some expressed puzzlement that the United States would consider military action against Iraq and not against North Korea, which claimed it already had nuclear weapons and had announced that it was willing to contemplate war with the United States. This criticism intensified when North Korea reportedly conducted a nuclear weapons test on October 9, 2006.

There was also criticism of Coalition policy by those who did not believe that military actions would help to fight terror, with some believing that it would actually help Al-Qaeda's recruitment efforts; others believed that the war and immediate post-war period would lead to a greatly increased risk that weapons of mass destruction would fall into the wrong hands (including Al-Qaeda).

Both inside and outside of the U.S., some argued that the Bush Administration's rationale for war was to gain control over Iraqi natural resources (primarily petroleum). These critics felt that the war would not help to reduce the threat of WMD proliferation, and that the real reason for the war was to secure control over the Iraqi oil fields at a time when US links with Saudi Arabia were seen to be at risk. "No blood for oil" was a popular protest cry prior to the invasion in March 2003. Administration officials denied these charges, and scholar Jeff Colgan writes that "there is still no consensus on the degree to which oil played a role" in the Iraq War.

Some opponents of the war also believed that there would be no weapons of mass destruction in Iraq, and thus there was little reason for an invasion. Prominent among these was Scott Ritter, a former U.S. military intelligence officer and then a United Nations weapons inspector in Iraq, and who in 1998 had been hawkish enough toward Iraq as to be admonished by U.S. senator Joe Biden, "The decision of whether or not the country should go to war is slightly above your pay grade." Investigations after the invasion failed to produce evidence of WMDs in Iraq (apart from a very small number of degraded chemical weapons shells located after the Iran–Iraq War ended in 1988). Generally, however, very few opponents of the Iraq invasion publicly expressed doubt as to whether the Saddam Hussein regime possessed weapons of mass destruction.

During the occupation, some opponents accused President Bush of being indifferent to the suffering caused by the invasion. In 2006 for example he opined that when the history of Iraq is written the period would "look like just a comma", prompting criticism that he took the more than 2,700 US troop deaths lightly.

Opposition in the United States

Popular opposition

The Iraq War was met with considerable popular opposition in the United States, beginning during the planning stages and continuing through the invasion subsequent occupation of Iraq. The months leading up to the war saw protests across the United States, the largest of which, held on February 15, 2003 involved about 300,000 to 400,000 protesters in New York City, with smaller numbers protesting in Seattle, San Francisco, Chicago, and other cities.

Consistent with the anti-war sentiment of the protests, in the months leading up to the Iraq War, American public opinion heavily favored a diplomatic solution over immediate military intervention. A January 2003 CBS News/New York Times poll found that 63% of Americans wanted President Bush to find a diplomatic solution to the Iraq situation, compared with 31% who favored immediate military intervention. That poll also found, however, that if diplomacy failed, support for military action to remove Saddam Hussein was above 60 percent.

Days before the March 20 invasion, a USA Today/CNN/Gallup Poll found support for the war was related to UN approval. Nearly six in 10 said they were ready for such an invasion "in the next week or two." But that support dropped off if the U.N. backing was not first obtained. If the U.N. Security Council were to reject a resolution paving the way for military action, only 54% of Americans favored a U.S. invasion. And if the Bush administration did not seek a final Security Council vote, support for a war dropped to 47%.

Immediately after the 2003 invasion most polls within the United States showed a substantial majority of Americans supporting war. In a March 2003 Gallup poll, the day after the invasion, 76% of Americans supported military action against Iraq, but that trend began to shift less than a year after the war began. Beginning in December 2004, polls have consistently shown that a majority thinks the invasion was a mistake. As of 2006, opinion on what the U.S. should do in Iraq is split, with a slight majority generally favoring setting a timetable for withdrawal, but against withdrawing immediately. However, in this area responses vary widely with the exact wording of the question.

After the invasion of Iraq, one of the most visible leaders of popular opposition in the U.S. was Cindy Sheehan, the mother of Casey Sheehan, a soldier killed in Iraq. Sheehan's role as an anti-war leader began with her camping out near President Bush's ranch in Crawford, Texas, and continued with a nationwide tour and trips to Europe and South America.

Opposition from national security and military personnel

Several prominent members of the military and national security communities, particularly those who favor a more realist approach to international relations, have been critical of both the decision to invade Iraq and the prosecution of the War.

On July 28, 2002, less than eight months before the invasion of Iraq,The Washington Post reported that "many senior U.S. military officers" including members of the Joint Chiefs of Staff opposed an invasion on the grounds that the policy of containment was working.Ricks, Thomas Some Top Military Brass Favor Status Quo in Iraq The Washington Post, July 28, 2002 p A01.

A few days later, Gen. Joseph P. Hoar (Ret.) warned the Senate Foreign Relations Committee that the invasion was risky and perhaps unnecessary.

Morton Halperin, a foreign policy expert with the Council on Foreign Relations and Center for American Progress warned that an invasion would increase the terrorist threat.

In a 2002 book, Scott Ritter, a Nuclear Weapons Inspector in Iraq from 1991 to 1998, argued against an invasion and expressed doubts about the Bush Administration's claims that Saddam Hussein had a WMD capability. He later accused the Bush administration of deliberately misleading the public.

I think [The Bush Administration] has stated that Iraq has weapons of mass destruction, and that's as simple as they want to keep it. They don't want to get into the nitty-gritty things such as if you bury a Scud missile to hide it from detection, there is a little thing called corrosion. Where do you hide the fuel, how do you make this stuff up, how do you align it. Because when you disassemble it, there is a process called re-alignment. There is a factory involved in that. And then you have to test launch it to make sure that the alignment works, and that's detectable, and they haven't done that. There is a lot of common sense things that go into consideration of whether or not Iraq has an operational weapons of mass destruction capability.