The antigovernment protests that erupted in Iran in the last days of 2017 showed that millions of Iranians are now disillusioned with the Islamic Republic. Moreover, there are signs that quite a few Iranians are now also disenchanted with Islam itself. Often silently and secretly, they are abandoning their faith. Some opt for other faiths, often Christianity.

This trend is being observed and reported, with understandable excitement, by Christian news sites. “Despite Regular Targeting and Imprisonment, Christianity in Iran Is Spreading,” the Iranian Christian news agency Mohabat News reported recently. The Christian Broadcasting Network, which transmits globally from Virginia, even declared, “Christianity is growing faster in the Islamic Republic of Iran than in any other country in the world.”

While a 2015 study by two researchers, Duane Alexander Miller of St. Mary’s University in San Antonio and Patrick Johnstone of WEC International in Singapore, estimated Iranian converts to Christianity from Islam from 1960 to 2010 at 100,000, it is hard to know the exact number. But the trend seems strong enough to worry Iran’s religious establishment — and make it turn to a solution it knows well: oppression.

The United States Commission on International Religious Freedom has reported that since 2010 more than 600 Christians in Iran have been arbitrarily detained. Iranian authorities have also raided services, threatened church members and imprisoned Christians, particularly evangelical Christian converts.