In the last throes of the insurgency...

rebels refine their bomb skills.

Insurgents have long been able to build bombs powerful enough to penetrate some armored vehicles. But the use of "shaped" charges could raise the threat considerably, military officials said. Since last month, at least three such bombs have been found, Lt. Gen. James T. Conway, the director of operations for the Joint Chiefs of Staff, told reporters at a Pentagon briefing this month.

The shaped charge explosion fires a projectile "at a very rapid rate, sufficient to penetrate certain levels of armor," General Conway said, adding that weapons employing shaped charges had caused American casualties in the last two months. He did not give details.

A Pentagon official involved in combating the devices said shaped charges seen so far appeared crude but required considerable expertise, suggesting insurgents were able to draw on well-trained bomb-makers, possibly even rocket scientists from the former government. Shaped charges and rocket engines are similar, the official said.

Infrared detonators are an advance over the more common method of rigging bombs to explode after an insurgent nearby presses a button on a cell phone, a garage-door opener or other device that gives off an electric signal. That approach is vulnerable to jammers, however, and a shift to infrared detonators, which rely on light waves, underscores the insurgents' resourcefulness.[Synaptic Sync emphasis]

Throes. Last. Indeed.