They've been the biggest killer of U.S. forces over several years of war in Iraq, but troops there are now seeing far fewer roadside bombs.

Not a single American or coalition service member was killed by an IED — improvised explosive device — in July, and none have died so far this month. By contrast, military deaths in Afghanistan have hit record levels due to a sharp jump in roadside bombings.

The chief U.S. military spokesman in Baghdad calls it a "dramatic" drop in Iraq. Brigadier General Steve Lanza tells The Associated Press it's due to a variety of factors. He says troops are better trained at avoiding the bombs and have better equipment for detecting them.

Lanza says U.S. and Iraqi forces are also working together to disrupt the networks that transport bomb materials. Since U.S. forces have moved out into the belts surrounding Iraqi cities, Lanza says they're able to keep more bombs from coming into urban centers.

While the drop is substantial, Lanza says the bombs remain a significant threat.