Ukraine could soon unleash robot dogs on its front lines, replacing soldiers for perilous missions like spying on Russian trenches or detecting mines. At a demonstration in an undisclosed part of Ukraine, the metallic dog known as model “BAD One” stood up, crouched, ran and jumped according to commands transmitted by its operator. Stealthy and agile, they could soon become an invaluable ally on the front line for a Ukrainian army that is short on manpower to repel the Russian invasion, its makers said.