Wikipedia begins by giving a somewhat moderate account of this essentially evil historical phenomenon. I say “evil” because genuine religious conversions arise from the heart rather than from external threats or perceived political gain.
The Inquisition was a group of institutions within the Catholic Church whose aim was to combat heresy, conducting trials of suspected heretics. Studies of the records have found that the overwhelming majority of sentences consisted of penances, but that cases of repeat unrepentant heretics were handed over to the secular courts, which generally resulted in execution or life imprisonment.
So rather than totally revise my entry for this topic, I will more or less leave it as it was in 2011, with an expansion regarding more recent feminist critiques:
In its more extreme forms, for which we have documented cases, the Inquisitions were a movement of organized and often cruel evil in which the Catholic Church or Catholic national leaders legally tried, tortured, and executed apparent heretics.
The legal tests for determining heretics were both irrational and usually predetermined by absurd experimenter bias.
In many instances, the authorities of the day were lawfully permitted to seize property formerly owned by a person branded as a heretic. All too often vulnerable widows suddenly became “heretics” once their deceased husbands had passed away. Thus it has been proposed, especially by feminists, that one motivation for accusing someone of heresy was greed, not spirituality.¹
Under Tomás de Torquemada (1420–1498) a horrific total of 2000 heretics were burnt at the stake, all on one occasion. Because of his penchant for torture and burning at the stake, “Torquemada’s name has become synonymous with cruelty, religious intolerance and fanaticism.”²
The Inquisition began around the 12th century in Southern France and Northern Italy and extended in various waves within Europe until finally abolished in Spain in 1834. The last execution also took place in Spain. In 1826 a teacher Cayetano Ripoll was executed for allegedly teaching Deism at his school.
¹ A similar dynamic of bullying the vulnerable can be seen around the world today whenever a respected or well-to-do spouse dies. If the survivor of that marriage, especially if a woman, is not wealthy or well-connected herself, she may fall into all sorts of political and economic difficulties. However, in some instances, a male survivor could also be harassed or persecuted. The key element is the loss of money, status and power, where the jackals once circling suddenly close in for the kill.
² https://en.wikipedia.org/wiki/Tom%C3%A1s_de_Torquemada
Related » Just War, Latin, Witches Hammer
Earthpages.org 
Edit – just made some very minor style tweaks. No change in meaning.
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