Every dictator needs their cronies on the ground in order to exert control over their population. Historically, the legwork behind most of the world's most-brutal regimes has been carried out by secret police forces, whose job it is to subjugate the populous and enforce their leader's policies. As far back as Ancient Rome, through to the Nazi Germany and as recently as in the last few years in dictatorships in Africa and the Caribbean, secret police forces have maintained order in a brutal and often arbitrary manner. No dictatorship could survive without a secret police force. However, not all secret police forces are the same. Their remits have differed over time - for example some serve solely as police forces, others take on intelligence roles, others are also paramilitary forces, while many perform executions on top of secret police work. The remit of a secret police force has been dependent on various factors, including the type of regime imposed, the era in which they were introduced, and the political climate present in the nation at the time. Here are the 10 most-feared police forces in the history of mankind - and let's just be thankful they are no longer around today...