Protests against the Iraq War
As soon as people became aware of the intentions of the United States and the Coalition of the Willing to start the Iraq War, a popular movement emerged to protest against the Iraq War. Opponents of the war organised a number of large-scale street protests including the worldwide anti-war protest on February 15, 2003, before major combat operations began. The London anti-war protest organised by the Stop the War Coalition had two million attendees. The February 15 protests have been recorded by the Guinness Book of World Records as the largest protest ever.
The protest movement drew on a number of ideological sources including pacifism, Islamism, anti-Americanism and strong feelings regarding the process by which the U.S. and the Coalition allies started the war unilaterally rather than through the processes of the United Nations and international laws and treaties.
U.S. neoconservatives, Charles Krauthammer and Robert Kagan, supporters of the policies of the George W. Bush Administration, agree multilateralism is the dominant view in Europe, and Europe opposes U.S. unilateralism.  Other U.S. analysts, such as the more centrist Richard Haass, now President of the Council on Foreign Relations, contrasted the multilaterally-waged 1991 Gulf War with the 2003 Iraq War, in a 2009 book entitled War of Necessity, War of Choice, contrasting his experience with two wars, under two Bushes, with one Iraq. He is one of the relatively few individuals to have been privy to the decisionmaking in both.
Representing the pacifist opposition to war were groups like the Campaign for Nuclear Disarmament, who helped organise the 2003 London protests with the Stop the War Coalition, and Quaker religious groups.
Many Muslims opposed the wars in both Afghanistan and Iraq, and some of that opposition went far enough that it has been described as "Islamist": the Muslim Association of Britain - a Stop the War Coalition member - is not widely considered to be radical or Islamist, but the protest movement has included people who have been influenced by radical Islamist groups and clerics such as Abu Hamza al-Masri.
Many feel that the protest movement was driven by anti-American and anti-globalization sentiment: much of the protest movement on the left was involved in the anti-globalization rallies against the World Trade Organization and the International Monetary Fund. The famous Battle for Seattle in 1999 is a prime example of this anti-globalization movement. Indymedia, a network of websites and independent media outlets set up and used heavily by the anti-globalization movement was used to promote the anti-war protest movement.
Opposition related to the process of getting UN resolutions - or the failure of the US and the Coalition to seek such resolutions in favor of unilateral action - drew others into the protest movement including a number of lawyers and intellectuals. Here, the objection was evidentialist rather than pacifist or "ideological" - the objectors argued that the U.S. and the Coalition had not presented the necessary evidence to either the population or the international community.
In contrast, the Afghanistan War (2001-) was much more of a consensus. The 9-11 Attack led to a quick invocation of the common defense article of the NATO Treaty. UN Security Council Resolution 1378, of 14 November 2001 (i.e., a month after the U.S. started military operations) certainly did not reject the action, "Supporting international efforts to root out terrorism, in keeping with the Charter of the United Nations, and reaffirming also its resolutions 1368 (2001) of 12 September 2001 and 1373 (2001) of 28 September 2001, Recognizing the urgency of the security and political situation in Afghanistan in light of the most recent developments, particularly in Kabul...Condemning the Taliban for allowing Afghanistan to be used as a base for the export of terrorism by the Al-Qaida network and other terrorist groups and for providing safe haven to Usama Bin Laden, Al-Qaida and others associated with them, and in this context supporting the efforts of the Afghan people to replace the Taliban regime..."
The 1999 Gulf War was even more of a multilateral action.
On 25 March 2003, Tony Blair observed "that after the war with Iraq there will be “a reckoning about the relations between America and Europe.” He took upon himself to discuss with President George W. Bush how to “get America and Europe working together as partners and not as rivals.” " Some European leaders stirred protest within a broader US-vs-Europe context. 
- "Gerhard Schroeder used strident anti-American rhetoric and opposition to war with Iraq in eking out a narrow victory in the Fall 2002 German elections.
- "French President Jacques Chirac elevated his disagreement with U.S. policy on Iraq to a broader quarrel over America’s role in world politics. Chirac viewed Iraq as a once and possibly future client for arms sales and influence, buttressed by his personal relationship with Saddam dating to the 1970s. Chirac also wished to avoid disturbances among French Muslims, a group the French government has begun to watch far more closely since last year. Differences with Washington over Iraq might have been resolved pragmatically, but the French leaders elevated the Iraqi disagreement into an extended conflict over the United States’ global role."
While street protests were less evident in the run-up to the war than in Europe, there were still significant policy debates. Some preceded the Iraq War, although were subsequent to the 9-11 Attack and Afghanistan War (2001-).
Neoconservative national strategy
Sometimes called the Bush doctrine as described in the document National Security Strategy of the United States of America (2002), and certainly described by neoconservative theoreticians, the United States had adopted a policy of preventive war.
The U.S. Congress was by no means unanimous in granting authorization for the war.
Many in the anti-war movement feel vindicated by the Downing Street Memos, and evidence that turned up in the investigation into the death of Dr David Kelly, which many feel show that the British government "sexed up" intelligence reports to make Iraq seem more of a threat than it turned out to be. The U.S. Iraq Survey Group report, also called the Duelfer Report or formally the Comprehensive Revised Report with Addendums on Iraq's Weapons of Mass Destruction, did not show significant weapons of mass destruction (WMD) capability in Iraq, although there was strategic intent on the part of Saddam Hussein.
While many factors were involved, opposition to the war played a role in the 2006 loss of U.S. Republican Party control of Congress and the 2008 loss of the White House. The restructuring of the U.S. political right is a response of unknown shape. There is much debate about long-term national security strategy, with rejection of neoconservative principles by some of its former advocates such as Francis Fukuyama in America at the Crossroads: Democracy, Power, and the Neoconservative Legacy, but also fervent defense by some.
- Robert Kagan (June 2002), "Power and Weakness", Policy Review
- Richard N. Haass (2009), War of Necessity, War of Choice: A Memoir of Two Iraq Wars, Simon & Schuster, ISBN 9781416549024, pp. 15-16
- William Hay (April 2003), "A Preliminary Reckoning: Prospects for U.S.-European Relations After Iraq", Foreign Policy Research Institute 4 (1)