Herbert Armstrong was a major cult leader of the Twentieth Century.
He was originally an ad copy writer, but was challenged by the teachings of the Church of God Seventh Day. He was 'converted' and took on the mantle of a minister of that church, only to find that he was not satisfied and needed to be independent, in charge of his own destiny and group, and not be subject to anyone else.
Herbert Armstrong founded the Radio Church of God based on the teachings of G. G. Rupert and set as a major doctrine, British Israelism as the teaching that the United States and British Commonwealth were lost tribes of ancient Israel -- a belief that has been thoroughly debunked -- and that this British Israelism was the Key to Prophecy, which then led him to become a great false prophet whose prophecies failed.
Herbert Armstrong went on to preach on radio as the voice of The World Tomorrow Program. He established Ambassador College which became the Headquarters in Pasadena, California for the Worldwide Church of God. He Published The Plain Truth as a recruiting tool and The Good News as an internal magazine for members and, later, coworkers (people who paid good money for his nonsense). He and his son, Garner Ted Armstrong, were the personalities on the World Tomorrow Telecast.
Herbert Armstrong determined that Christians (cult members of his sect) needed to keep the Old Testament Israelite Feasts to gain salvation, but transformed them from celebrations with animal sacrifices to Church Cult Corporate Conventions for which members paid by saving another 10% of their gross income as Second Tithe -- a practice never supported even by Old Testament standards (tithing was to be kept using 10% of produce and was never based on wages).
Interested parties may read and review the flip book in this section to ascertain the full impact of the folly of Herbert Armstrong.