I agree here. One of the wonderful aspects of most Western-style societies is that the military and police are made up of people who are citizens first and foremost. The militaries in these societies are loyal to the populous first, and the government second. They will certain follow government orders, but only to a limit. If Britain or Germany ordered their soldiers to occupy a city and shoot anyone out after a certain curfew, the military would simply refuse and the government would collapse.
In order to get to a position where that kind of oppression is possible, the society needs to change in such a manner so that the military and police authorities are loyal to the government first and the people second. This is generally done by giving them economic benefits and freedoms that are not available to the rest of the population. As noted by yesdachi, this is radically different from the way most Western societies work today. That doesn't mean it isn't possible for those societies to change in this manner, but their very nature prevents radical changes on this level. In order for these societies to become capable of systematic oppression of a large number of people, there needs to be a gradual erosion of the safeguards which prevent it. It is for this reason that it is simply impossible to imagine the US Army inflicting a brutal crackdown on dissidents today, but it is theoretically plausible to imagine it 100 years from now.
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