 According to Gabriel Kolko about 12,000 suspected opponents of Diệm were killed between 1955 and 1957 and by the end of 1958 an estimated 40,000 political prisoners had been jailed.By the end of 1959, Diệm was able to entirely control each family and the communists had to suffer their "darkest period" in their history.Membership declined by two thirds and they had almost no power in the countryside of South Vietnam.