In later periods, this term was used to describe any Shi'i group not accepted by the Zaydis, orthodox Twelvers, and sometimes the Ismailis.
Najran, a fertile valley in what is now southwestern Saudi Arabia at the foot of mountains bordering the vast stretch of desert known as the Empty Quarter, was traditionally home to Christian and Jewish communities, in addition to Sulaymani Ismailis and Zaidis.
The conflict has its roots in an insurgency against the government of Yemen which was initiated by the Zaidi religious leader Hussein Badreddin al-Houthi in 2004.
In 1175, he drove out the Hamdanid emir, Ali ibn Hakim al-Wahid, from Sana'a after the latter's army was weakened by continuous raids from the Zaidi tribes of Sa'dah.