Yemen is one of the oldest centers of civilization in the Near East. Its capital and largest city is Sana'a. Yemen's territory includes more than 200 islands, the largest of which is Socotra, about 354 km (220 mi) to the south of mainland Yemen. It is the only state in the Arabian Peninsula to have a purely republican form of government. Yemen was the first country in the Arabian peninsula to grant women the right to vote. Yemeni unification took place on 22 May 1990, when North Yemen was united with South Yemen, forming the Republic of Yemen.
The majority of Yemen's population is divided into tribal groups, especially in the northern areas of the country where 85% of local residents belong to various tribes There are also small groups of peoples of Turkish/Ottoman origin in urban areas. Roughly 55% of the population are Sunni Muslims following the Shafi'i school while 45% adhere to the Zaydi Shia branch of Islam with small minorities of Ismali Muslims. Since the 1990s, the Houthis (an armed Zaydi group) has attempted to establish Zaydi Shia principles in the