Answer
World War II led to the expansion of Chabad-Lubavitch, a Hasidic Jewish movement, under the leadership of Rabbi Menachem Mendel Schneerson. During the war, Schneerson's predecessor, Rabbi Yosef Yitzchak Schneersohn, was imprisoned in the Soviet Union, and Schneerson assumed leadership of the movement. After the war, Schneerson worked tirelessly to rebuild and expand Chabad-Lubavitch, establishing educational institutions, outreach centers, and synagogues around the world.