"The major role of the eunuch in ancient societies was a political one. Eunuchs were the perfect guardians of harems and provided safe companions and secretaries for royal ladies. They could also be entrusted with the very highest offices of state with no fear that they would want to muscle in and start their own dynasties. Less susceptible than other men to corruption and persuasion by sexual means, they were the ideal politicians and civil servants. Their reputations could not be sullied by the accusations of rape, paternity suits and other scandals that so often blight the careers of public figures."
"The first civilization deliberately to select eunuchs as officers of state was the Assyrian Empire, which dominated the Near East during the early first millenium BC. The practice was continued by its successors, including the Persian Empire, founded by Cyrus the Great (559-529 BC) who, according to the Greek writer Xenophon, 'selected eunuchs for every post of personal service to him, from the doorkeepers up'. Eunuchs were becoming powerful in China during the same period. They were especially influential under the Han Dynasty (202 BC - 220 AD), when some held tremendous power simply because of their looks, and it was normal for emperors to have as many male favorites as the recommended magical number of wives. But most were of the professional variety, trained for a career in government."
"The Roman civil service also employed eunuchs, despite the bans on castration imposed by various emperors. And, although the custom was condemned by the Church, the zenith of 'eunuch power' in the Roman world actually came after it was Christianized, under the Eastern Roman (Byzantyne) Empire, which ruled from Constantinople (Istanbul) between AD 395 and 1453. Thousands of young men entered public service by being castrated, providing the empire with some of its most distinguished state secretaries, generals and even Church leaders."
Quoted from: "Ancient Inventions", Peter James and Nick Thorpe, 1994. Image: the Roman castration clamp, an invention that enabled much safer castration than earlier methods by avoiding damage to the penis.