Zaidi theology differs from Isma'ilism and Twelver Shi'ism by stressing the presence of an active and visible imam as leader.

[2] Although he did not succeed in establishing any permanent administrative infrastructure, al-Hadi's descendants, and other Alid clans who arrived in his company, became the local aristocracy of the northern highlands.

The imams were usually chosen from the offspring of al-Qasim ar-Rassi and more specifically of al-Hadi, but on at least eight occasions they were picked from other lines descending from Muhammad's grandsons Hasan and Husain.

Meanwhile, a multitude of smaller dynasties and families established themselves in the highlands, as well as in the Tihamah (the low coastal plain) where the imams rarely gained influence.

Ironically, the Sunni Rasulids, who eventually concentrated their rule in southern Yemen for precisely that reason, were the dynasty under which the region experienced the greatest economic growth and political stability.

From the early seventeenth century al-Mansur al-Qasim, belonging to one of the Rassid branches (later known as the Qasimids or Yemeni Zaidi State), raised the standard of rebellion.

His son al-Mu'ayyad Muhammad managed to gather the entire Yemen under his authority, expel the Turks, and establish an independent political entity.

[9] The power of the Yemeni Zaidi State or Imamate declined in the eighteenth and nineteenth centuries, especially in the wake of the Wahhabi invasions after 1800.

[10] The territory controlled by the imams shrank successively after 1681, and the lucrative coffee trade declined with new producers in other parts of the world.

While Yemen under the two imams seemed almost frozen in time, a small but increasing number of Yemenis became aware of the contrast between an autocratic society they saw as stagnant and the political and economic modernization occurring in other parts of the world.

In 1965 Egyptian president Gamal Abdel Nasser met with King Faisal of Saudi Arabia to consider a possible settlement to the civil war.

The meeting resulted in an agreement whereby both countries pledged to end their involvement and allow the people of North Yemen to choose their own government.

[14] In June 1974 military officers led by Colonel Ibrahim al-Hamdi staged a bloodless coup, claiming that the government of Al-Iryani had become ineffective.

Saleh strengthened the political system, while an influx of foreign aid and the discovery of oil in North Yemen held out the prospect of economic expansion and development.

Among the wars of Imam Yahya Hamid al-dain and his son Ahmad against the Zaraniq tribes, from 1925 until 1929, and the expropriation of their money and property as booty.

To the Qawqar massacre in late 1967, to suppress the uprising of the Zaraniq protesting, against the return of the Imamate in a new form following the coup of November 5, 1967, supported by the tribal leaders and who arranged for him to involve the royalists in the rule, as the conditions of the people in Tihama worsened, after those leaders made the Tihama a spoil, and practiced all forms of humiliation and domination of its people.