The Mihna: Inquisition on the Quran's Nature

Caliph al-Ma'mun imposed the Mu'tazili doctrine that the Quran was created, testing scholars and imprisoning those who refused. Imam Ahmad ibn Hanbal famously resisted, enduring flogging and imprisonment for two years. The Mihna lasted 15 years until Caliph al-Mutawakkil ended it, restoring the traditional Sunni position.