To quote Asimov: "Its dependence upon the outer worlds for food and, indeed, for all necessities of life, made Trantor increasingly vulnerable to conquest by s

To quote Asimov: "Its dependence upon the outer worlds for food and, indeed, for all necessities of life, made Trantor increasingly vulnerable to conquest by siege. In the last millennium of the Empire, the monotonously numerous revolts made Emperor after Emperor conscious of this, and Imperial policy became little more than the protection of Trantor's delicate jugular vein".