Yosef Yitzchak (Joseph Isaac) Schneersohn was an Orthodox rabbi and the sixth Rebbe (spiritual leader) of the Chabad Lubavitch chasidic movement. After many years of fighting to keep Orthodox Judaism alive from within the Soviet Union, he was forced to leave; he continued to conduct the struggle from Latvia, and then Poland, and eventually the United States, where he spent the last ten years of his life.

Source: Wikipedia