The division began as a question about succession — whether leadership after the Prophet's death in 632 belonged to the community's choice or to his family through Ali — and hardened over the following century into two traditions with distinct hadith corpora, legal schools, devotional calendars and theological emphases. Sunnis are roughly 85 percent of Muslims and Shia roughly 12, with Twelvers the large majority of the latter and Ismailis, Zaydis and others making up the rest. The geographic concentration is Iran, Iraq, Azerbaijan, Bahrain, Lebanon, and substantial minorities in Pakistan, India, Saudi Arabia's Eastern Province, Yemen and Afghanistan. The important historical correction is that sustained sectarian violence is not the default state: for long stretches and in many cities the two communities lived intermarried and interleaved. What has driven the modern violence is state competition — the Iran–Saudi rivalry after 1979, the sectarian architecture of post-2003 Iraq, the Syrian war, the Yemen war — and militant movements that treat Shia Muslims as apostates. Ordinary Sunni jurisprudence does not, and the 2005 Amman Message said so explicitly.