WASHINGTON - The shrinking U.S. combat role in Afghanistan has given insurgents an opening to devise and carry out deadlier attacks using bigger improvised bombs against U.S. and coalition military vehicles and bases, American officials say.

With fewer U.S. forces patrolling road networks beyond their bases - and with the grounding of eye-in-the-sky surveillance balloons known as aerostats - Taliban fighters are adapting their tactics, according to officials at a Pentagon agency that tracks attacks that use improvised explosive devices, or IEDs.

"Insurgents are able to invest more time in preparing and staging an attack, and when we see an effective attack, it tends to be more lethal to our forces," said Al Sweetser, chief of the operations-analysis division at the Joint IED Defeat Organization.

So while the number of IED attacks against U.S. and coalition troops - as well as the total casualties they cause - has declined, certain attacks can be more elaborately planned, precisely targeted and more lethal because the insurgents have time and room to prepare, Sweetser and other American officials said.

The Pentagon has invested billions of dollars to develop gadgets, such as hand-held ground-penetrating radar systems, and techniques to find IEDs before they explode and to mitigate damage from those that can't be stopped. The evolving struggle began a decade ago in Iraq with insurgent groups countering high-tech U.S. weapons with relatively cheap and surprisingly effective methods of killing and maiming. A hallmark of the insurgents' use of IEDs in Afghanistan has been their ability to adapt to changing circumstances.

A recent IED strike near the southern provincial capital of Kandahar killed five American soldiers in an armored vehicle in one of the more deadly examples of how the Taliban have taken advantage of a changing military landscape.

Insurgents took the time and effort to tunnel underground and place an unusually large IED well below the surface, said David Small, spokesman for the counter-IED agency.

U.S. Toll in Afghanistan





Latest identifications

• 1st Lt. Jonam Russell, 25, of Cornville, Ariz.

• Sgt. Stefan M. Smith, 24, of Glennville, Ga.

• Spc. Rob L. Nichols, 24, of Colorado Springs, Colo.

All three were assigned to the 3rd Battalion, 15th Infantry Regiment, 4th Infantry Brigade Combat Team, 3rd Infantry Division, Fort Stewart, Ga.

Source: Department of Defense