US Marines test fired a dozen rockets from a mobile launcher on Wednesday at a range in the foothills of Japan's iconic Mount Fuji, in an exercise to keep sharp on weapon that is a growingly important component of the American military's arsenal.The High Mobility Artillery Rocket System (HIMARS) is a launcher mounted on the back of a military truck that can be rapidly brought out from concealment, fire its rockets, then move quickly to a new location to avoid counter-battery fire.The so-called "shoot and scoot" tactics are becoming increasingly important with the proliferation of drones over the battlefield, which…