Some quotes from Rick Atkinson's article linked above:

Read the whole thing.

IED Blitz would focus as many forms of surveillance as possible in a "persistent stare" at a bomb-infested 20-kilometer stretch of Route Tampa, just south of Balad on the road to Baghdad. The blitz would enlist satellites, U-2 spy planes, 14 Mako unmanned aerial vehicles, a pair of larger I-Gnat drones, and the Horned Owl, a Beechcraft turboprop airplane equipped with ground-penetrating radar used to assess whether road shoulders had been disturbed by digging.

Attacks had grown increasingly extravagant, with "daisy-chained" munitions that included as many as 22 artillery shells wired together to explode simultaneously in a 300-yard "kill zone." Intelligence analysts assumed that such ambush sites took hours or even days to prepare. On the basis of past attack patterns, they predicted that 60 IEDs would be planted in 75 days on this short segment of Route Tampa.

Hundreds of thousands of photographs would be snapped as part of a technique called "coherent change detection." Two images of the same scene taken at different times would be compared, pixel by pixel, to spot changes in the landscape -- such as the anomalies caused by an insurgent planting a bomb. Ground convoys could be warned, and, if the reconnaissance was nimble, hunter-killer teams could flush emplacers or triggermen.

The operation, estimated to cost at least $3 million, would be directed from Defense Department offices leased in Fairfax County.
Blitz began on Tuesday, Aug. 24, 2004. So brilliant were the digital color images that analysts could read the brand names on plastic water bottles littering the roadside. They could distinguish an apple from a pomegranate at a fruit stand.

What they could not see was a bomb or a bomber.


The most disheartening day came on Thursday, Nov. 4. By chance, virtually all surveillance assets -- satellites, U-2s, drones -- happened to be focused simultaneously on one small swatch of Route Tampa. Traffic appeared normal. Two hours later, another sequence of images revealed a scorched crater where a bag of artillery shells triggered by a detonation wire had just killed one American soldier in a truck and severed the leg of another. Dozens of photos showed the burning vehicle veer across the median, and rescue vehicles convene at the site. No images revealed the IED being placed, or the triggerman.

Analysts soon surmised that bomber cells around Balad in late summer had shifted "to a just-in-time device-placement method," as a Defense Intelligence Agency analyst put it. Instead of requiring hours or days to survey an ambush site and bury a device, "hasty emplacement" took two hours or less.

Blitz ended on Nov. 15. In 10 weeks, 44 IEDs had detonated or were discovered by ground clearance teams. Asked how many had been detected by aerial surveillance, the Air Force officer said, "To be honest with you, I can't say any of them.

"We had only a 20-kilometer stretch," the officer added. "There are thousands of kilometers in Iraq."
This is why I get nervous anytime someone tells me the tech in FCS or Air power will solve my problems through ROVER or any other gimmick. We focused almost national asset and tech available, plus hundreds of personnel on twenty klicks of road and were unable to stop or identify attacks.