It was billed by the US military as "the largest air assault operation" since the overthrow of Saddam Hussein in 2003, with attack and assault aircraft providing "aerial weapons support" for 1,500 US and Iraqi commandos moving in to clear "a suspected insurgent operating area north-east of Samarra."
By Jim Muir
BBC News, Baghdad
The early release of video and stills of the operation was unusual
The international news agencies immediately rang the urgent bells on the story.
Around the world, programmes were interrupted as screens flashed the news, which dominated the global media agenda for the next 12 hours or more.
On the New York Stock Exchange, oil prices jumped $1.41 (£0.80) a barrel "with a massive US-led air assault in Iraq intensifying jitters about global supplies of crude", as one agency reported it.
By the middle of Day Two in the ongoing operation, it was clear from both US and Iraqi military sources that the advance had met no resistance.
There were no clashes with insurgents. No casualties were reported.
In what was clearly a combing operation using cordon-and-search tactics in a patch of remote desert terrain with scattered farms and homesteads, military spokesmen said the advancing forces uncovered six caches containing arms, explosives and other insurgent material.
They detained 48 people, of whom 17 were freed without delay. Officials said they did not believe they had captured any significant insurgent leaders.
"Any leaders there must have seen the forces coming, and escaped," said one senior Iraqi security source.
By the middle of Day Two, the operation had already been scaled down to 900 men.
Operation Swarmer clearly bore no comparison in scale to the initial attack which brought down Saddam Hussein's regime, or to the massive assault on the insurgent stronghold in the city of Falluja in November 2004.
US military pictures showed troops involved in the operation
Nor did it appear to match a series of counter-insurgency operations involving air strikes and ground forces in remote areas near the Syrian border in western Iraq last year.
In one four-day campaign last May, the US military said it had killed 125 insurgents for the loss of nine of its own men killed and 40 injured.
So how and why did this latest apparently routine combing operation, yielding a few arms caches and netting some low-grade suspects, manage to win stop-press coverage around the world?
The use of the phrase "the largest air assault operation" was clearly crucial, raising visions of a massive bombing campaign.
In fact, all the phrase meant is that more helicopters were deployed to airlift the troops into the area than in previous such operations.
The 50 "aircraft" that had been deployed were not combat jets blasting insurgent targets, but helicopters ferrying in the forces. There was no rocketing or bombing from the sky.
In US military parlance, "air assault" means transporting troops into a combat zone by air. It could include, but does not necessarily imply, air strikes.
Question of semantics?
A US military spokesman gave the BBC the following official definition of the term:
The US military says some 1,500 US and Iraqi troops are involved
"According to US joint (multiservice) doctrine, an air assault is one in which assault forces, using the mobility of rotary wing assets and total integration of available firepower, manoeuvre under the control of a ground or air manoeuvre commander to engage enemy forces or seize key terrain."
In this instance, key terrain may have been seized, but no enemy forces were apparently engaged.
But the massive press coverage was not just the result of a semantic misunderstanding.
Unusually, high-quality photographs and video footage of the initial deployment were made available to the press towards the end of Day One of what was billed as a campaign that would last several days.
Some international media were given unusually swift military embeds to the area.
As the announcement about Operation Swarmer pointed out, a roughly similar campaign had been conducted earlier this month in the area to the west of Samarra.
"Operation Swarmer follows closely the completion of a combined Iraqi-Coalition operation west of Samarra in early March that yielded substantial enemy weapons and equipment caches," it said.
Open to speculation
That operation, yielding similar results, received no coverage at all. Nor did it shake the New York Stock Exchange.
The operation is targeting suspected insurgents near Samarra
The name of Samarra has entered the Iraqi annals as a turning-point in the current strife.
The destruction of the Shia Imam al-Askari shrine there on 22 February triggered a wave of sectarian violence in which hundreds died.
Operation Swarmer was aimed at sweeping any insurgents out of an area north-east of Samarra where, local residents said, they had been active.
It was part of an ongoing campaign against the militants.
The reasons for it being given such high-profile publicity are clearly open to speculation.
The operation came at a time when support at home for President Bush and his campaign in Iraq is running very low, and when the international media were preparing to focus on the third anniversary of the war, just three days later.