Of all the savage innovations of the 20th century, the most sinister may be the quota for state criminals. I believe this policy was introduced by Stalin's henchman Nikolai Yezhov, who in the aftermath of the first purge trials set every NKVD district a quota of anti-Soviet criminals to arrest and interrogate. The quotas totaled more than a million for the whole USSR. Half a million people were shot, more than a million sent to the Gulag. Policemen who did not fill their quotas were sent to the Gulag themselves.
I just learned this morning that Mao used the same approach during his 1957 purge of "rightists" within the party. He required the head of every party unit to denounce 5% of his or her underlings as rightists. Those denounced were expelled from the party, fired from their jobs, and sent to do hard labor in the countryside. This sounds less severe than Stalin's Gulags, and it was probably intended to be, but in practice these suspicious people were highly vulnerable and when the massive famine of the "Great Leap Forward" hit China in 1959-1961 many of them were among the 30 million Chinese who starved to death.
The thinking behind these measures escapes me. I can certainly understand arresting opponents of the regime, but what is gained by imposing a quota? Surely everyone knew this would lead to the arrest of many innocents. Was that the point? To make state terror something as random and uncontrollable as the wrath of God, as likely to take the innocent as the guilty? Was the point to implicate the police or party leaders by forcing them to either hand over innocents or be handed over themselves? The fusion of bureaucracy with the worst cruelty was one of the signal achievements of the century, and for me these quotas sum up perfectly the dark absurdity of totalitarianism.