That would be the reign of the Anabaptists (German: Wiedertäufer, re-baptizers) in the German city of Münster from February 1534 to June 1535. It was pretty gruesome. Here is their leader Jan van Leiden (1509-1536) beheading Elisabeth Wantscherer, one of his 16 wives, because she criticized him.
The Anabaptists became their own variation of Protestant Christianity in the early years of the Reformation. The Reformation is conventionally dated to 1517 when Martin Luther (1483-1546) publicly presented his famous 95 Theses. Luther was excommunicated from the Catholic Church as of January 1, 1519, and proceeded to establish Protestant Churches in those domains where the local prince (or other ruler) was so disposed. By 1523, Ulrich Zwingli (1484-1531) had established his variant of Protestantism in Zürich. John Calvin (1509-1564) openly adopted the Protestant teaching in 1535 and would later found his own brand of Protestant theocracy in Geneva.
Martin Luther (1483-1546)
The Anabaptists were a sect that began in Zwingli’s Zürich. They began in 1524 to practice their distinct doctrine against baptizing infants against the practice prescribed by the state in defiance of the city authorities. The re-baptizing part of their group's label came from the fact that they insisted that infant baptism was completely illegitimate and that anyone baptized as an infant had to be baptized again as an adult.
Ulrich Zwingli (1484-1531)
Expelled from Zürich, they spread their doctrine in the southwestern parts of Germany and the Netherlands. Melchior Hofmann (1500-1543/4), a mystic with an apocalyptic vision name, joined with the Anabaptists in 1530 in Strasbourg (in France today) and became their most influential leader. He believed the world would end in 1533 and that therefore it was the urgent task of Christians to establish the Kingdom of God immediately on earth. After Melchior was imprisoned in Strasbourg in 1533, another apocalyptic mystic named Jan Matthys (d. 1534) became the primary leader of the Dutch Anabaptists.
John Calvin (1509-1564)
When Dutch authorities began suppressing the Anabaptists, Matthys decided on establishing a theocratic New Jerusalem in Münster, where the Kingdom of God would be established in advance of the rapidly approaching Second Coming of Christ. Until early 1534, the Anabaptists had been peaceful, even explicitly pacifist. They seized political control of Münster in February 1534 with the help of local converts and Anabaptists immigrants from the Netherlands.
Jan Matthys (d. 1534), Anabaptist prophet and martyr
The Catholic bishops called on Philipp of Hessen to suppress the Münster Anabaptists and announced a blockade of the city. This was the breaking point when the pacifist Anabaptists became holy warriors. Lead by the preachers Matthys and Bernt Rothmann (c. 1495-c. 1535) and the joint mayors Gerd Kibbenbrock and Bernt Knipperdolling (d. 1536), the Anabaptists prepared to defend the city amid outbreaks of ecstatic spirituality and prophecies among their number.
Bernt Knipperdolling (d. 1536)
They seriously plundered the Catholic churches and other Catholic institutions of the city. A particular target was paintings and images of the Catholic saints and the Virgin Mary, which they considered idolatrous. But their plunder wasn’t random. They destroyed the towers on most churches to use the materials to fortify the city walls, but left one tower standing to provide surveillance of approaching troops.
Jan van Leiden performs an adult baptism in New Jerusalem
Then they expelled all the unbelievers, i.e., those who declined to be re-baptized and join the Anabaptists, and seized their property. Most cities weren’t that big at the time, and after the expulsion of around 2,000 who refused to join with the Anabaptists, they were left with over 5,000 adult women and around 2,000 adult men. So the Anabaptists adopted polygamy in the New Jerusalem. Adopting a radically new family system understandably caused considerable discontent. Even though the normal marriage age was lower then in Europe than today, when the Anabaptists started marrying off 11-year-old girls, that was pretty unusual.
As the first painting above illustrates, a large female majority didn't mean democratic empowerment of women or a rollback of patriarchal attitudes. Other than the Elisabeth Wantscherer, who wished to leave the city because of the food crisis and criticized her husband the king's policies, the voices of the female majority seem to have been almost completely lost to history.
Images of the Virgin Mary: the Anabaptists didn't approve
On Easter Sunday, Matthys led a group of lightly-armed followers out to confront of hostile mercenaries just outside the city, perhaps thinking that there would be some supernatural intervention of their behalf. Matthys and most of the group were slaughtered, and his head impaled and displayed outside the city.
Jan van Leiden then became the main leader of the city theocracy. He proclaimed himself King of the New Jerusalem and appeared at religious services seated on a gilded throne with two young men at his side, one holding the Bible and the other a sword. When a group of dissidents kidnapped him with the intent to overthrow him in July 1534, his followers fought to free him. After he had regained control, he had 47 of the conspirators publicly executed in the main city plaza.
It was Van Leiden that initiated polygamy in the city. Despite his taste for personal pomp, he also enforced a kind of radical egalitarianism in property, including limiting the amount of clothes people could own. Excess clothing was taken from the wealthier citizens and distributed to the poor. Money was banned for internal usage in the city and everyone's money confiscated to buy supplies from outside the city. The possession of all books except the Bible was banned, and the sinful volumes burned in a huge bonfire. These measures were take out of some combination of principle and the expectation of the imminent End of the World. The psychological dynamics that we see in cults today was no doubt also at work, though social conditions and relationship patterns were different enough then that any comparison with today's cults should be a cautious one.
Bishop Franz von Waldeck, holy warrior
New Jerusalem was able to repel two attempts by the hostile forces outside to take the city. But in 1535, Bishop Franz von Waldeck began preparations for a new assault. The blockade was taking its toll by causing severe food shortages, which drove some residents including some of the men to leave the city. When the bishop’s forces quickly took the city on June 25, 1535, they displayed their own version of Christian mercy by carrying on three days of slaughter, with 650 left dead.
The end of Jan van Leiden, King of New Jerusalem
Jan van Leiden and other surviving leaders were imprisoned. Van Leiden and two others were executed six months later by having the flesh torn from their bones piece by piece with hot iron pincers in a four-hour public spectacle. What was left of their bodies were displayed in cages on the front of the church tower.
The Amish: more benign spiritual descendants of the Anabaptists
As with other fanatical sects whose influence outlived their early and most fanatical phase, the Anabaptists’ spiritual legacy continued in less apocalyptic manifestations. The Mennonites, the Amish and today’s Baptists are all influenced in some significant way by the Anabaptists, though today’s Baptists don’t belong to the Anabaptists’ direct historical tradition. A less-well-known sect still survives whose tradition also extends back to the Anabaptists is the Hutterite Brethren.
The remains of Van Leiden and two others were displayed in cages on the church tower
There is going to be a musical (?!) staged later this year in Münster about the group, Wiedertäufer - Das Musical. There is also an opera loosely based on the life of Jan van Leiden, Le Prophète [The Prophet] by Giacomo Meyerbeer, first performed in 1849.
(My account here is based in particular on that by Nicolas Büchse, "Das Neue Jerusalem", in Martin Luther und die Reformation - GeoEpoche 39/2009)