Vilna Gaon
Antagonism to Hasidism

When Hasidic Judaism became influential in Vilna, the Vilna Gaon joined rabbis and heads of the Polish communities, to speak against Hasidic influence.

In 1781, when the Hasidim renewed their proselytizing work under the leadership of their Rabbi Shneur Zalman of Liadi (the "Ba'al Ha'tanya"), the Gaon excommunicated them again, declaring them to be heretics with whom no pious Jew might intermarry.
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