Answer:
   
   The Chassidic movement started in the 1700's (Common Era) in Eastern
   Europe in response to a void felt by many average observant Jews of
   the day. The founder of Chassidism, Rabbi Israel Baal Shem Tov
   (referred to as the "Besht," an acronym of his name) was a great
   scholar and mystic, devoted to both the revealed, outer aspect, and
   hidden, inner aspect of Torah. He and his followers, without veering
   from a commitment to Torah, created a way of Jewish life that
   emphasized the ability of all Jews to grow closer to G-d via
   everything that we do, say, and think. In contrast to the somewhat
   intellectual style of the mainstream Jewish leaders of his day and
   their emphasis on the primacy of Torah study, the Besht emphasized a
   constant focus on attachment to G-d and Torah no matter what one is
   involved with.
   
   After the Besht died in 1760, the leadership of the second generation
   of the movement passed to Dov Baer of Mezhirech. From his court
   students went forth who were successful in attracting many scholars to
   Chassidism and sending them to the master at Mezhirech to absorb his
   teaching. By the 1830s the main surge of the spread of Chassidism was
   over. By this time, it had become the way of life of the majority of
   Jews in the Ukraine, Galicia, and central Poland, and had sizable
   groups of followers in Belorussia-Lithuania and Hungary. With the
   great waves of emigration to the West from 1881, Chassidism was
   carried into Western Europe and especially to the United States.
   
   Early on, there was a schism between the Chassidic and non-Chassidic
   (i.e. Misnagdim, lit. 'opponents') Jewish movements, primarily over
   real or imagined issues of halachic observance. The opposition was
   based on concern that the Chassidim were neglecting the laws regarding
   appropriate times for prayer, and perhaps concern about the exuberance
   of Chassidic worship, or a concern that it might be an offshoot of
   false messiahs Shabbtai Zvi or Jacob Frank. Within a generation or two
   the rift was closed. Since then, many Chassidic practices have
   influenced the Misnagdim, while the Misnagdim, in turn, moderated some
   of the extremes of early Chassidism. Nevertheless, the dispute between
   particular groups of Chassidim and Misnagdim continues to this day,
   especially in Israel, and occasionally on soc.culture.jewish.
   
   In the period leading up to World War II, various chassidic sects
   entered the political life of modern states. However, after 1850 the
   expansion of Chassidism stopped. The ideas of the Enlightenment,
   national and socialist ideals, and the Zionist movements shook the
   traditional Jewish way of life. Chassidism opposed any change in the
   way of life and sheltered itself from new forces in Judaism.
   
   During the Holocaust the chassidic centers of Eastern Europe were
   destroyed. The masses of Chassidim perished and, together with them,
   most of the chassidic leaders. Many who survived who survived moved to
   Israel or America, and established new chassidic centers. In parallel,
   the philosophy of Martin Buber and Abraham Joshua Heschel, and the
   works of writers such as Peretz helped to mold a new generation of
   Chassidism, which had a considerable influence on modern Jewish
   culture and youth. Although some sects have remained self-segregated,
   many sects have become part of everyday modern life. Since the 1970s,
   Chassidism have maintained a period of expansion and development.
   
   Today, Chassidim are differentiated from other Orthodox Jews by their
   devotion to a dynastic leader (referred to as a "Rebbe"), their
   wearing of distinctive clothing, and a greater than average study of
   the inner aspects of Torah.
   
   There are perhaps a dozen major Chassidic movements today, the best
   known of which (with perhaps 100,000 followers) is the Lubavitch group
   headquartered in Brooklyn NY. Other groups include the Bobov,
   Bostoner, Belzer, Gerer, Satmar, Vizhnitz, Breslov, Puppa, Bianer,
   Munkacz, and Rimnitz. In Israel, the major Chassidic groups after the
   Lubavitch group are: Gor (-Gerer), Viznitz, and Bealz (=Belzer).
   
   Additional information may be found in the [5]Chasidism Reading List,
   available at http://www.scjfaq.org/rl/joc-index.html.