In a cramped workshop near the front in northeastern Ukraine, military mechanic “Chimera” is helping prepare his unit’s robot forces for battle. Lined up in a row, the four-wheeled unmanned vehicles known as “Hyenas” will crawl towards Russian lines with their payload of explosives and attack an enemy dugout or halt an advance. Similar models have captured Russian prisoners, said Chimera, 44, who asked to be identified by his call sign. “Imagine what 20kg (44 pounds) of explosives is like: it’s...