When did the Sunni-Shiite division occur?

Answer 1

The divisions started in 632, after the death of Mohammed. It is largely about the succession of power. The shi'a believed that the successor should be a member of Mohammed's family and the Sunni's believed that it should be someone the community believed to be the best leader. The Sunni's won the first go around, but assassinations, wars and other means of conflict have continued for centuries.