This north-south distinction existed among the tribes of the Arabian Peninsula since pre-Islamic times (before the 7th century). However, there is no mention of hostility between the two groupings in pre-Islamic Arab tradition. The Qays did not function as a tribal confederation before the advent of Islam, and in ancient Arab histories, the tribes that would form the confederation were mentioned individually rather than as a collective. According to historian W. Montgomery Watt, it was during the Umayyad era (638-750), that the Arab tribes began organizing themselves along northern (Qaysi) and southern (Yamani) lines so as to constitute something like a political party. The rivalry between Yaman and Qays may have stemmed from competition over grazing rights in Syria following the conquest. However, open conflict between them occurred only during the Second Muslim Civil War (680-692).