Bertolt Meyer pulls off his left forearm and gives it to me. It’s smooth and black, and the hand has a clear silicone cover, like an iPhone case. Beneath the rubbery skin are skeletal robotic fingers ...

At 5 o’clock on a blistering morning in June 2007, U.S. Marine Cpl. William Gadsby helped lead a team of infantrymen into the farmland surrounding Karma, an agricultural hub in Iraq’s volatile Anbar ...