He could soon become a soldier’s best friend, following them faithfully across the battlefield, and even carrying their equipment. US military bosses today showed off the latest version of their robot dog, named LS3 but dubbed AlphaDog, a four-legged, autonomous robot that can follow a soldier. The machine, one of a series designed by Boston Dynamics, can stand upright, walk for 20 miles without a break and carry up to 400 pounds.