BAGHDAD - Explosives tore at another Iraqi bridge Tuesday, demonstrating once again how much easier it is to crumble this country's infrastructure than it is to protect it or rebuild it.
The blast was at least the 12th in the last three months in what appears to be an effort to cut off the traffic arteries that allow Iraqis and U.S. troops to move about the country.
Military experts differ on whether the bridge bombings have any tactical significance. They could create chokepoints that clog U.S. supply convoys and isolate sectarian groups. However, they also restrict how insurgents move, and American troops can travel by air.
There's broader agreement that the sabotage makes the U.S. military and its flailing Iraqi government allies look powerless to protect even the country's basic infrastructure, let alone put Iraq on a course to recovery.
The closings of river crossings and thoroughfares keep ordinary Iraqis cooped up in their neighborhoods and homes, wary of venturing over bridges that might be targeted or taking dodgy detours.
They express frustration at the insurgents who are ripping at their country's battered infrastructure and the supposedly powerful government that can't safeguard bridges.
"The state has no will and no strength," said Basel Jasem, a 55-year-old furniture store owner and former army officer. "(And) the terrorists want to control things by isolating Baghdad."
As bridge bombings go, Tuesday's was relatively tame. It came at about 7:30 a.m., apparently injured no one and, while inflicting significant damage, left open a single lane on the crossing between the villages of al Qariya al Asriyah and al Rashayed in Babil province, about 35 miles south of Baghdad.
But it came on the heels of attacks Sunday and Monday - including one six miles away - and was the latest in a string of bridge bombings that started in March.
A truck bomb on Monday badly damaged a bridge across the Diyala River in Baqouba, 35 miles northeast of Baghdad. That forced traffic to travel through an area where al-Qaida-linked groups pose a grave threat.
The bridge attacks have killed scores of people and increased the danger in Iraq in ways incalculable yet tangible.
Bookstore worker Sayf Adel said he wouldn't cross two bridges near his Karradah neighborhood in central Baghdad "for a billion dinars."
When his family left Baghdad recently to visit Islamic shrines in Karbala, a fallen bridge meant a longer route and a brush with gunfire. Adel quit his job with one of the country's largest cell-phone companies after the Sarafiyah bridge over the Tigris River in northern Baghdad collapsed from the blast of a suicide truck bomb April 12.
"They exploded the bridge to make us use the long way, so it would be easier to kill people," Adel said.
Military analysts said the series of attacks highlighted one strength an insurgency had on its side: persistence.
"(The bridges') destruction causes disruption to everyday life," said Owen Cote, the associate director of the security studies program at the Massachusetts Institute of Technology. "The goal of the insurgents is to demonstrate that we can't be everywhere at once and that they can keep this up as long as the occupation lasts, no matter how much we surge."
Others said that by limiting transportation routes, insurgents funneled American targets onto fewer and more predictable routes and forced troops to restrict civilian traffic.
"It reduces the ability of reinforcements and quick reaction forces to move efficiently," said Nathan Hughes, a military analyst for Stratfor Forecasting. "Coalition forces will continue to prioritize their own access, (which is) unlikely to win any hearts and minds," he said.
A U.S. intelligence official said the targeting of bridges around Baghdad appeared to be part of a strategy by Sunni Muslim insurgents to stoke public anger at the Shiite Muslim-dominated government of Prime Minister Nouri al-Maliki and the U.S. military.
"If you . . . isolate portions of Baghdad, that would have an obvious complicating effect on the surge," said the U.S. intelligence official, who asked not to be identified because of the sensitivity of the issue.
A senior U.S. military officer in Baghdad, speaking on condition of anonymity because he isn't authorized to discuss the issue publicly, said "we have a significant military advantage whether they knock out a bridge or not. . . . It probably does more along the psychological lines than militarily. The psychological effect shows the government can't do certain things."
Insurgents have attacked oil pipelines and water and electrical facilities throughout the war, devastating the government's ability to keep basic services running.
The bridge attacks come against a backdrop of rising violence. May was one of the bloodiest months for Iraqis and American troops since the United States invaded in 2003. American generals warn that this summer could see even more violence as insurgents attempt to discourage the U.S. presence.
Jonathan S. Landay in Washington and special correspondent Laith Hammoudi in Baghdad contributed to this report.