 Abbasid civil war (865–866)

The Abbasid civil war of 865–866, sometimes known as the Fifth Fitna, was an armed conflict during the "Anarchy at Samarra" between the rival caliphs al-Musta'in and al-Mu'tazz, fought to determine who would gain control over the Abbasid Caliphate.The war, which lasted for about a year, largely revolved around a prolonged siege of Baghdad and ended with al-Mu'tazz as sole caliph.