The twentieth century was one of the darkest and most deadly in all of human history. Vast amounts of blood were spilled and people subjected to the most terrible fear and oppression. Such dictators as Hitler, Stalin, Pol Pot and Idi Amin inflicted genocide on millions. Hitler had those whom he regarded as “useless" exterminated in the gas chambers. Hundreds of thousands of people in many Western countries—from Great Britain to Germany, from the USA to Sweden—were compulsorily sterilized or left to die just for being sick, crippled or old. All over the world, people were oppressed and exploited because of ruthless competition. Racism became the ideology of certain states, and some races were not even regarded as human at all.