In April 2003, BBC political editor Andrew Marr made an effusive broadcast from the steps of Number 10 Downing Street. Earlier that day, less than a month after their initial invasion, coalition forces had taken Iraq’s capital. As Marr gleefully reported, the mood inside the British prime minister’s office was one of elation.

The capture of Baghdad, he announced, had put an end to “the faint air of pointlessness” and stench of “tawdry arguments and scandals” that had been hanging over the prime minister. All doubts about Tony Blair, his government, and the assault on Iraq, Marr proclaimed, could be safely consigned to history’s dustbin. In praising Blair, he then threw all caution to the wind:

Mr Blair is well aware that all his critics out there in the party and beyond aren’t going to thank him — because they’re only human — for being right when they’ve been wrong. And he knows that there might be trouble ahead, as I said. But I think this is very, very important for him. It gives him a new freedom and a new self-confidence. . . . I don’t think anybody after this is going to be able to say of Tony Blair that he is somebody who is driven by the drift of public opinion or focus groups or opinion polls. He took all of those on. . . . It would be entirely ungracious, even for [Blair’s] critics, not to acknowledge that tonight he stands as a larger man and a stronger prime minister as a result.

Nearly twenty years later, the episode continues to stand out as emblematic. In the lead-up to the war and through its early months, mainstream journalists and liberal pundits on both sides of the Atlantic not only jettisoned the reflexive skepticism that is supposedly central to their trade but, in many cases, any pretense to objectivity whatsoever.

Here was Marr, political editor of Britain’s influential public broadcaster, sounding off as if he worked in Blair’s comms department: gushing earnestly about the PM’s courage; chastising those, like the country’s former foreign secretary Robin Cook, who had possessed the chutzpah to question the wisdom of the invasion; and even celebrating that Blair, ostensibly the leader of a democracy, had faced down the massive public mobilizations against the war.

In doing so, Marr was certainly not alone. While British journalists and commentators — spanning the Murdoch press to liberal newspapers like the Guardian and the Observer — fell dutifully in line, their US counterparts arguably went even further.

For months on end, citizens were hit with a relentless barrage of jingoism matched only in its salivating intensity by statements from the Bush administration itself. For much of the time, as obsequious TV anchors and pundits regurgitated pro-war talking points, even this distinction between an independent press and the administration was blurred.

At mainstream outlets, antiwar voices were scant, and the few that did exist were quickly silenced. In the two-week period surrounding then secretary of state Colin Powell’s now infamous presentation at the United Nations, an astonishing 76 percent of guests on major cable networks were either current or former military or government officials. Of some 267 guests, according to a 2003 analysis by Fairness and Accuracy in Reporting, only one tepidly expressed any reservations about the possibility of war. Across America’s op-ed pages, meanwhile, commentators like David Brooks, Thomas Friedman, and Jonathan Chait penned hawkish editorials in support of the Bush administration’s position and denounced its opponents as useful idiots, or worse.

This chorus was amplified by reporters all too happy to launder unconfirmed information from anonymous sources — who most often turned out to be officials as well — only to have the reports cited by the administration as independent verification of its case. Through this process of “stove-piping,” as it was memorably dubbed by investigative journalist Seymour Hersh, the institutions of the US media and state generated a feedback loop of hyperbole and false information that was subsequently served to the public with the sheen of objective truth.

The result was that, by March 2003, considerable majorities of Americans not only believed Iraq possessed (or was on the cusp of developing) nonexistent weapons of mass destruction (WMDs), but that Saddam Hussein had played a role in the September 2001 attacks.

None of these things, needless to say, was remotely true. And yet, in the lead-up to the invasion and into its early months, large swathes of the mainstream media effectively deputized themselves to promote the narrative regardless. Twenty years later, there is a widespread perception that the principal sources of misinformation can be found in foreign governments and obscure recesses of the internet. The sinister experience of 2003, however, reminds us that mainstream outlets were deeply complicit in popularizing claims for which there was absolutely no evidence — and misleading countless millions with a fraudulent case for war.