The organization has exhaustively chronicled the abuses of Saddam Hussein's regime dating back to the 1980s, estimating it was responsible for as many as 250,000 deaths. But it says in a lead article in its annual survey of human rights that at the time of the U.S.-led invasion last March, there was no crisis in Iraq that justified a massive military intervention.
Human Rights Watch also says the United States and its allies failed to pursue at least one key nonmilitary option -- a criminal prosecution of Hussein.
"The justification for humanitarian intervention has to be the real, current threat that is there," he said. "Otherwise, you have the chance of just launching wars left, right, and center, frankly, when a powerful government feels that it is in its power, in its right, to launch a war. And that's the really dangerous pattern that's being set."
The report said the international community missed an opportunity to unseat Hussein nonmilitarily through an international indictment.
It said the recent experiences of former Yugoslav President Slobodan Milosevic, who is now facing war crimes charges in The Hague, and former Liberian President Charles Taylor, who fled the country last year, indicate that an international indictment can serve to undermine dictators.
Crawshaw of Human Rights Watch says, "We would absolutely argue that more could have been done, for example, in terms of prosecution and justice and wasn't, and I think that's something that governments need to reflect on. They shouldn't immediately be grasping for the war option as the first option. It should absolutely be the last option, not the first option."
U.S. and British leaders have said the invasion was prompted by concern over Iraq's weapons of mass destruction. They said Hussein was given 12 years under mounting Security Council resolutions to prove it had eliminated its weapons of mass destruction.
Ahead of the Iraq invasion, they withdrew a draft resolution that sought explicit Security Council support for action against Iraq. But U.S. and British officials say their actions were already supported by previous Security Council resolutions. They have also justified the war on humanitarian grounds.
No weapons of mass destruction have yet been found in Iraq. The U.S.-led invasion of Iraq is supported by Nile Gardiner, a fellow at the Heritage Foundation, a conservative policy institute in Washington.
"Had the U.S. and Britain not taken military action, Saddam Hussein would have remained in power for decades longer. His family would no doubt have ruled Iraq for generations to come. You simply cannot rely on international indictments or the United Nations or international criminal courts to remove dictators from power. Sometimes, you have to take military action to do so."
Gardiner tells RFE/RL that organizations such as Human Rights Watch should be heralding the ouster of Hussein. "The Iraqi people are immensely better off now that Saddam Hussein is gone, and it is quite extraordinary that a leading human-rights watchdog is claiming that this was the wrong thing for the West to do."
Lee Hamilton is a former U.S. congressman who served on an international commission that explored the issue of humanitarian interventions. Its 2001 report -- titled "The Responsibility to Protect" -- said that states have a duty to protect their citizens from avoidable catastrophes, but that if they cannot, the international community must assume the responsibility.
Hamilton tells RFE/RL that there was legal and moral justification for the war to oust Hussein. But he said the issue was complicated by what he called the "questionable premise" under which the war was originally mounted.
Hamilton, who directs the Woodrow Wilson International Center, says the experience in Iraq points out the gulf that exists between Washington and much of the international community about the use of force.
The debate on humanitarian intervention, notably supported by UN Secretary-General Kofi Annan in a 1999 speech, continues to evolve. But Hamilton said he cannot envision the United States ever giving up the option of acting unilaterally on matters it sees as central to its security: "It's a huge divide between, basically, Americans and everybody else. There would be some exceptions, but most countries today would argue that if there's going to be intervention, it ought to be authorized by the United Nations. I can't conceive of any American president agreeing to that."
The Human Rights Watch report also faults the international community for disengaging from Afghanistan. The report joins the appeal made by UN and Afghan officials for the International Security Assistance Force to expand beyond Kabul in meaningful numbers.
It also charges the United States is giving power to regional warlords to help maintain stability. Crawshaw of Human Rights Watch expressed concern that the rising influence of warlords and waning international influence could return Afghanistan to its dark period of widespread factional unrest.
"[The warlords] are receiving money and weapons in order to be, if you like, the local policemen." he said. "Well, this is simply compounding the difficulties that we have got."
U.S. officials stress that they are expanding the security presence through Provincial Reconstruction Teams, which mount civilian projects but can call on military support when necessary. Germany, New Zealand, and Britain are contributing to these teams.
The Human Rights Watch report also criticizes European and U.S. governments for failing to maintain pressure on Russia to curb rights abuses in Chechnya. It said last year that a cycle of arbitrary detention, torture, and forced disappearances had become entrenched in the republic.
Russia's interlocutors, the report said, need to deliver a unified message calling for accountability for crimes against civilians and access to the region by human-rights monitors.