A war-weary American public that a year ago resoundingly rejected US military intervention in Syria to overthrow the Assad regime now is rallying behind the use of force to destroy the so-called Islamic State (Isis). In just three months, from June to September, support for US airstrikes in Iraq soared from 45% percent to 71%, and to 65% for airstrikes in Syria.

How did such an astounding turnabout occur? Certainly it wasn’t due to the persuasive powers of President Obama, who seems to have been reluctantly dragged into a conflict that he once acknowledged has no military solution.

The credit for selling Obama’s war on Isis must go to the mainstream American media.

Day after day, night after night, the press relied on propaganda from both Isis and the US government to whip up fear and a thirst for revenge in the American public. Gruesome beheading videos distributed by Isis were played over and over. The media not only regurgitated official US messages but packaged them better than the government itself ever could.

And then, as if Isis wasn’t enough to whip up public fear itself, the Khorasan Group suddenly appeared as the US media compliantly latched onto the new script leaked by anonymous officials, just a few days before Syrian air strikes were set to begin. Khorasan, they told the public on the administration’s behalf, is a group of hardened terrorists more dangerous than Isis because it plans to attack commercial planes using flammable clothing or exploding toothpaste.

The imminent Khorasan attack justified the ensuing U.S. bombing. However, it was later reported that Khorasan – if it even exists – is just a handful of militants whose plans were not so imminent. Few media bothered to follow up on that aspect of the story.

Why has the media pushed the Obama administration’s war frame instead of playing the role of skeptic by questioning official assertions, insisting for corroboration on “anonymous leaks” and seeking alternative points of view? After years of government lies – from claims of WMDs in Iraq to zero civilian casualties in drone strikes – you’d think the members of the fourth estate would have learned a lesson.

But the mainstream US media plays the role of government lapdog more than watchdog.

They sensationalized the supposed threat from Isis even as intelligence agencies insisted that the group poses no immediate threat to the United States. A chorus of fearmongers, Republicans and Democrats alike, appeared on TV to insist that the American way of life is at stake. The hysterical Senator Lindsey Graham claimed that Isis is out to murder each and every one of us. Senator Bill Nelson advocated cutting off the “head of the snake” before Isis could fly its black flag over the White House. Former CIA and Pentagon chief Leon Panetta warned Americans to brace for a 30-year crusade. The media even trotted out “experts” on war – or at least war-mongering – like John McCain, Dick Cheney and even former presidential envoy to Iraq, Paul Bremer.

Obsessed with maintaining access to power, the mainstream media just keeps handing their megaphone to the powerful and self-interested. Rarely do we hear from people who opposed the disastrous 2003 invasion of Iraq or rightly predicted the chaos that would result from NATO intervention in Libya. The few anti-war voices who manage to slip into the dialogue are marginalized and later silenced.

Let’s face it: fear sells, violence sells, war sells. The vicious Isis beheadings, discussed ad infinitum, attracted large audiences. So did talk about exploding toothpaste. People whipped into a state of fear always want to know more.

Sadly, the public is not getting what it deserves: a well-rounded debate about the pros and cons of military action. Why has a decade of support for the Iraqi army and years of covert CIA support for the Syrian opposition been so fruitless? How much might this intervention cost? (So far, the bill has been more than $1bn.) How will Middle East monarchies that funded extremists suddenly become exemplars of democratic values? What is the endgame in Syria? Will Bashar Assad still be in power? What are the unintended consequences of expanding American military action in the Middle East? (The Israeli newspaper Haaretz reported that the US bombings already have attracted 6,000 more recruits to Isis.) And most important of all: what are the alternatives to stop the slaughter of innocent civilians? The voices of people proposing political solutions other than slaughter are the voices the public deserves to hear.

Wars usually start with overwhelming public approval once the White House and the national security apparatus get the media to beat the war drums. It’s only after people tire of war that the media really begin to seek answers to questions that should have been asked before the bombs were launched.

But instead, once again, the US government and the US media establishment is embracing a military policy of airstrikes to strengthen local capacity despite a regional landscape – from Yemen to Libya – littered with the wreckage of this approach. Smoldering in the detritus of war is also the fourth estate.