Who was the fourth Caliph?

1. Hazrat Usman (R.A.)
2. Hazrat Ali (R.A.)
3. Hazrat Umar (R.A.),
4. Hazrat Abu Bakar (R.A.)

Hazrat Ali ibn Abi Talib (R.A.) became the 4th Rightly Guided Caliph in 656 CE (35 AH) after Hazrat Usman’s (R.A.) martyrdom. His caliphate witnessed the First Fitna (civil war), including the Battle of the Camel (656 CE) and Battle of Siffin (657 CE). A cousin and son-in-law of Prophet Muhammad ﷺ, he established Kufa as his capital and was martyred in 661 CE (40 AH) by a Kharijite assassin. His reign solidified Islamic jurisprudence through landmark judgments preserved in Nahj al-Balagha.