History of Jehovah's Witnesses
Jehovah's Witnesses originated as a branch of the Bible Student movement, which developed in the United States in the 1870s among followers of Christian Restorationist minister Charles Taze Russell. Bible Student missionaries were sent to England in 1881 and the first overseas branch was opened in London in 1900. The group took on the name International Bible Students Association and by 1914 it was also active in Canada, Germany, Australia and other countries. The movement split into several rival organizations after Russell's death in 1916, with one—led by Russell's successor, Joseph "Judge" Rutherford—retaining control of both his magazine, "The Watch Tower", and his legal and publishing corporation, the Watch Tower Bible and Tract Society of Pennsylvania.
Bible Student movement
Bible Students who submitted to Rutherford's leadership of the Watch Tower Bible and Tract Society became known as "Jehovah's witnesses" in 1931. The Watch Tower Society remains the denomination's primary administrative body, and their beliefs and organizational structure have diverged considerably from Russell's. Their literature states that "Bible Students" is the former name for their group, and does not acknowledge the continued existence of other Bible Student groups. In 1955, the Watch Tower Society claimed that those who separated from the movement during Rutherford's presidency constituted the "evil slave" of Matthew 24:48-51. (The Society altered its view in 2013, calling the "evil slave" a hypothetical warning to the 'faithful slave'.) Jehovah's Witnesses report worldwide membership of over 8 million.