For decades, DARPA, the secretive research arm of the Department of Defense, has dreamed of turning soldiers into cyborgs. And now it’s finally happening. The agency has funded projects that involve implanting chips into soldiers’ brains that could one day enhance performance on the battlefield and repair traumatized brains once the fog of war has lifted. “Of the 2.5 million Americans who served in Iraq and Afghanistan, 300,000 of them came home with traumatic brain injury,” journalist Annie Jacobsen told NPR. “DARPA initiated a series of programs to help cognitive functioning, to repair some of this damage. And those programs...