The implosion of the U.S. mission in Afghanistan and the quick takeover of the country by the Taliban has led to considerable hand-wringing over what went wrong. Was it insufficient commitment to nation building, diminished by war with Iraq? Or was a federal Afghan government never viable in a country where political power is mostly tribal, regional and ethnic?

Yet, a responsible reckoning must also appreciate the foresight of those who opposed the U.S. war in Afghanistan all along, no matter how managed. Remarkably prescient, these antiwar voices hold powerful lessons about the hazard of dismissing reasoned dissent.

The night of Sep. 11, 2001, President George W. Bush declared that “our very freedom came under attack” in “evil, despicable acts of terror.” “We will make no distinction,” he intoned, “between those who committed these acts and those who harbor them.” With these and other words, within days, Bush set the template for America’s response to 9/11: to wage a global war, in the name of virtue and the 9/11 dead, against evil enemies and their enablers.

Beginning Oct. 7, the first great strike came in Afghanistan, meant to take out both al-Qaeda and the Taliban regime that hosted it. Overwhelmingly, the American public supported the war, which toppled the Taliban by early December. Approval topped 90 percent.

And yet, some Americans disagreed. Their paramount concern was civilian casualties. Inevitable in any war, the prospect had particular significance in the Afghanistan campaign. The essential wrong of 9/11, after all, was the cruel targeting of civilian lives. The death of innocents at American hands, whether by errant bombs or in the fog of war, would undercut the war’s moral purpose.

“Let us not add to the inhumanity of our times,” pleaded a family bereaved on 9/11, fearful that Afghan families would suffer as it had. “Craig would not have wanted a violent response to avenge his death,” Amber Amundson, widowed on 9/11, insisted in a letter to Bush. The threat of becoming “the evil that we deplore” prompted Rep. Barbara Lee (D-Calif.) to cast the sole “no” vote on congressional authorization for war.

A related fear was that a U.S. attack would feed a cycle of violence nearly impossible to break. “For every ‘terrorist’ or his ‘supporter’ that is killed,” the Indian intellectual Arundhati Roy wrote two weeks into the bombing, “hundreds of innocent people are being killed too. And for every hundred innocent people killed, there is a good chance that several future terrorists will be created.”

Noam Chomsky warned that 9/11 was a “diabolical trap” set by Osama bin Laden to lure America into a country famously unkind to infidel occupiers. Journalist Robert Scheer spelled out the risks. “The Taliban,” he predicted, “will retreat to its caves, ready to fight an endless war of attrition, and the fundamental questions facing the U.S.-led coalition will be the same: Is it possible to install any Afghan government with a popular base and sufficient integrity to rule? Can this new leadership keep the battle-hardened Taliban in check militarily? If not, is the U.S. public prepared for the possibility of an endless and costly quagmire?” Roy cautioned that the war “will develop a … logic and a justification of its own, and we’ll lose sight of why it’s being fought in the first place.”

Opponents of war pushed for alternatives. They argued that the 9/11 attacks were criminal acts demanding a response based in justice, not vengeance. “Nations governed by the rule of law investigate crimes, arrest criminals, hold trials,” asserted the left-wing journalist Laura Flanders. By means of diplomacy or police action, the United States could capture the 9/11 perpetrators and try them in a proper international court. America would both lead and win by demonstrating, against al-Qaeda’s depravity, its commitment to democratic values.

Viewed from 20 years out, these antiwar arguments foretold much of the mess in Afghanistan. U.S. bombs killed civilians in private homes and weddings, while the CIA set up torture sites on Afghan soil. This violence, in part, fueled the insurgency, mitigating the good America also did the country. Long ago, Americans lost both a sense of the war’s purpose and any appetite for quagmire.

The U.S. bloodlessly capturing bin Laden and trying him in court may have scarcely been a realistic possibility. But the idea points to the problem of making a chronic enemy of the Taliban. Its two-decade war was to expel the American occupiers and retake political power, not threaten the United States with terrorism.

Antiwar voices ran into enormous head winds. A traumatized nation desperate for security and payback put its faith in an administration primed for war. Arguments against war were never given serious consideration by the government, much of the media and the American public. Instead, they were commonly castigated as naive, unpatriotic or even appeasing terrorists. The swift, apparent end of the war in early 2002 further blunted the antiwar cause, only to restart as the Bush administration threatened a new, more controversial war in Iraq.

Bush described 9/11 as an assault on America’s democratic “way of life.” Yet the country never practiced the genuine deliberation — when it mattered most on a subject so grave as war — that is the hallmark of democracy. America thus deprived itself of the chance to look before leaping into a conflict holding enormous challenges and risks. Instead, now, two decades later, the United States scrambles to end the war, leaving behind both allies and honor.