The US Army is building a laser weapon over a million times more powerful than any used before – although because it delivers short pulses, the overall energy involved is low.

Existing laser weapons produce a continuous beam that is held on a target, such as a drone or missile, until it melts – the first was deployed by the US Navy in 2014 . The new weapon, known as the Tactical Ultrashort Pulsed Laser for Army Platforms , would be more like science-fiction movie lasers, firing bullet-like pulses of light.

Such …