U.S. Troops Still Train on Weapons With Known Risk of Brain Injury

A blast shattered the stillness of a meadow in the Ozark Mountains on an autumn afternoon. Then another, and another, and another, until the whole meadow was in flames.

Special Operations troops were training with rocket launchers again.

Each operator held a launch tube on his shoulder, a few inches from his head, then took aim and sent a rocket flying at 500 miles an hour. And each launch sent a shock wave whipping through every cell in the operator’s brain.

For generations, the military assumed that this kind of...