When it comes to insurgent attacks in Iraq, the only pattern is that there may be no pattern.
The recent upsurge in Iraqi violence, after a relative lull following national elections, has left US officials and outside experts alike groping for answers about the nature of the enemy. It's possible that the attacks are meant to take advantage of the new Iraqi government's struggles to organize itself, for instance. But it is at least as likely that the increase has been powered by reasons known only to the insurgents themselves, such as flagging morale or an increase in the availability of fighters or weapons.
Even to speak of "an insurgency" is something of a misnomer, as there are probably a number of insurgencies, split between foreign jihadis, die-hard Saddam Hussein followers, and anti-American opportunists. One expert compares them to a flock of birds or a school of fish who suddenly group, travel in formation, and then disperse - all without any central command.
"And with birds and fish, who knows where they are going to go?" says Itamara Lochard, a specialist in insurgencies at Tufts University's Fletcher School in Medford, Mass.
On Tuesday the US military continued to engage insurgent fighters in the fiercest fighting of the occupation since US forces retook the city of Fallujah.
For a third day, Marines, backed by extensive air power, swept through western Iraq near the Syrian border - an area in which insurgents, particularly foreign insurgents motivated by a desire for anti-American jihad, had operated with some impunity for months.
The offensive, named Operation Matador, had killed as many as 100 insurgents since Sunday, claimed US officials. US casualties were said to be light.
The fighting comes amidst a surge in suicide bombings and other insurgent attacks that began to take shape in late March. Those attacks continued Tuesday, as well, with the explosion of at least two car bombs in central Baghdad.
The last 10 days to two weeks has seen an increase in car bombs, detonated both remotely and by drivers, said Lt. Gen. James T. Conway, director, Joint Operations, Joint Staff, at a Pentagon briefing on May 5.
It is possible that this increase reflects an increase in activity on the part of the foreign jihadis, as suicide attacks have long been part of their operational pattern. It is also possible that the bombers are native Iraqis who have been forced into a desperate move by the kidnapping of loved ones, said General Conway.
"We're asking ourselves, what's all this mean? And we don't have the answers yet," he added.
The insurgency has been watching and learning from US tactics, say military officials. Take the roadside bomb, long the insurgent weapon of choice. It began with small mortar shells rigged to explode. That evolved into larger artillery shells, followed by explosive devices composed of 500-pound bombs and antitank mines.
"As we've added armor, they've added greater explosives," said Brig. Gen. William Catto, commanding general, Marine Corps Systems Command, at a House Armed Services Committee hearing last week.
The upsurge in violence has come as the newly-elected Iraqi government struggles to constitute itself in a manner acceptable to the country's main factions - Sunnis, Shiites, and Kurds. The juxtaposition of these things has led many to conclude that the insurgents are trying to take advantage of perceived chaos to try to terrorize the population.
That could be the case. As Itamara Lochard of the Fletcher School notes, if there is any common goal among insurgent groups, it is that they want to return to the pre-invasion status quo.
But in truth neither the US nor the Iraqis themselves understand the rhythms of the fighting in the country, according to Council on Foreign Relations president emeritus Leslie Gelb.
Mr. Gelb recently returned from a 10-day trip to Iraq, during which he met and interviewed many of the country's new leaders, as well as US officials. One of his main conclusions from this experience was that no one knows what is going on.
"The people I spoke with there ... they couldn't figure out why there had been a lull in violence for the last few months and then an eruption, what was going on with the various insurgent groups, and when it would end, or why it would end," said Gelb in remarks posted on the Council on Foreign Relations website.
The good news may be that the insurgents have no strong unifying theme around which to rally a significant portion of Iraq.
The Baathist portion of the insurgency wants to restore Saddam-like rule. The Islamist portion presumably longs for some kind of theocracy. Neither of these visions appeal to a majority of Iraqis, says retired Maj. Gen. William Nash. That is why there are indications that a growing number of average Iraqis are beginning to cooperate with their nascent government in tracking down these forces.
"The insurgency itself does not have a powerful message that is the future," says General Nash, now director of the Council on Foreign Relation's Center for Preventive Action.