Complex sentence: As communist rule spread in Vietnam after the Vietnam war, open practice of the Bahá'í Faith was banned from 1975 to 1992, and the number of believers dropped sharply during this time until in 2007 there were but 6880 known Bahá'ís.
Split into simpler sentences: As communist rule spread in Vietnam after the Vietnam war, open practice of the Bahá'í Faith was banned from 1975 to 1992. The number of believers dropped sharply during this time of proscription until in 2007 there were but 6880 known Bahá'ís.