The Muslim Ummah
Sectarian violence persists to this day from Pakistan to Yemen and is a major element of friction throughout the Middle East

Battle of Siffin
May–July 657 CE) occurred during the First Fitna, or first Muslim civil war, with the main engagement taking place from July 26 to July 28. It was fought between Ali ibn Abi Talib and Muawiyah I, on the banks of the Euphrates river,