More than a quarter of all US soldiers evacuated from Iraq and Afghanistan to DC’s Walter Reed Army Medical Center have traumatic brain injury—a percentage higher than in any prior war or conflict.

Explosions from landmines, grenades, and IEDs, or improvised explosive devices, cause the most injuries in Iraq. A blast can rain debris down on a soldier’s head or throw him off his feet—movements that can shake the brain inside the skull, bruising the brain or tearing fibers connecting brain cells.

Just as air bags have helped more people walk away from car accidents, improved body armor means more soldiers are surviving attacks that once might have killed them. Better diagnosis may also account for some of the brain injury increase.

“Society has gotten more sophisticated about mild traumatic brain injury,” says Dr. Deborah Warden, director of the Defense and Veterans Brain Injury Center, based at Walter Reed. “We’re able to diagnose more.”

In 1992, with funding from Congress, the Defense and Veterans Head Injury Program was founded. Warden says there’s now a military infrastructure for recognizing and treating brain injury, and centers around the country that specialize in treating these patients, including one at Walter Reed. In the field, Warden says, there’s better training too. “After an explosion, medics know to check out anybody who was exposed,” she says.

In January 2006, Bob Woodruff, who had just been named co-anchor of ABC World News Tonight, suffered a traumatic brain injury while with the military in Iraq. He and his wife, Lee, have written a book, In an Instant, about his recovery. It is due out February 27.