Bellus IV was a planet on which a war was fought between humans and robots.
When the Seventh Doctor arrived a human commander, Deldran, took him quickly to the human headquarters. There, the remnants of a great experiment to simply turn off the robots had been halted by the death of the chief scientist. The Doctor finished the work, flipped the switch — and promptly discovered that the "human" side were robots, too. As he powered down for good, Deldran explained that the humans had died ages before, leaving the war running by robot proxy. When Deldran used his last bit of power to explain that the robots wouldn't have known what to do with peace, the Doctor echoed the sentiment, wondering if anyone was really built for peace. (COMIC: War World!)