Islamic sectarian conflict
A number of insurgencies worldwide set Muslims against Muslims, or against Muslim-related religions such as the Baha'i Faith, rather than Muslim against non-Muslim. Some set one major sect against another, such as Sunni, the majority, versus Shi'a. Others are based on interpretation strictness within a sect, such as Salafism within Sunnism. Yet others may nominally be the same sect, but divided on ethnicity, such as Arab Sunni versus Kurdish Sunni in Iraq, or Baqqara nomadic Arabs versus Fur pastoralists in the Darfur conflict.
Takfir is a concept within Sunni Islam, which is often first directed at the government of current Muslim states that are insufficiently pure in being guided by Shari'a. It was a motivation, for example, of Egyptian Islamic Jihad (EIJ). Indeed, it can be traced back to Ibn Tamiyya and his fatwa allowing jihad against the Mongols, who still used tribal law although they considered themselves Muslims.
One Shi'a concept is the theocracy embraced by Ayatollah Ruhollah Khomeini and the 1979 Islamic Revolution in Iran: wilayat al-faqih (the rule of the jurisprudent). In Iraq, the mainstream 'marji'iyya, or collection of marji' (Shi'a jurist and theologian), recognized a leading spiritual authority, Grand Ayatollah Ali Sistani, the leading marji' in Iraq, as marji' al-Taqlid, who did not see his role as political.