For the next 44 years North Yemen was ruled by two powerful imams. Imam Yahya ibn Muhammad and his son Ahmad created a king-state there much as the kings of England and France had done centuries earlier. The two imams strengthened the state and secured its borders. They used the imamate to insulate Yemen and revitalize its Islamic culture and society at a time when traditional societies around the world were declining under imperial rule. 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. This produced an important chain of events: the birth of the nationalist Free Yemeni Movement in the mid-1940s, an aborted 1948 revolution in which Imam Yahya was killed, a failed 1955 coup against Imam Ahmad, and finally, the 1962 revolution in which the imam was deposed by a group of nationalist officers and the Yemen Arab Republic (YAR) was proclaimed under the leadership of Abdullah al-Sallal.

The first five years of President Al-Sallal's rule, from 1962 to 1967, comprised the first chapter in the history of North Yemen. Marked by the revolution that began it, this period witnessed a lengthy civil war between Yemeni republican forces, based in the cities and supported by Egypt, and the royalist supporters of the deposed imam, backed by Saudi Arabia and Jordan. 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. Subsequent peace conferences were ineffectual, however, and fighting flared up again in 1966.

By 1967 the war had reached a stalemate, and the republicans had split into opposing factions concerning relations with Egypt and Saudi Arabia. In late 1967 Al-Sallal's government was overthrown and he was replaced as president by Abdul Rahman al-Iryani. Fighting continued until 1970, when Saudi Arabia halted its aid to royalists and established diplomatic ties with North Yemen. Al-Iryani effected the long-sought truce between republican and royalist forces, and presided over the adoption of a democratic constitution in 1970.

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. The constitution was suspended, and executive power was vested in a command council, dominated by the military. Al-Hamdi chaired the council and attempted to strengthen and restructure politics in North Yemen. Al-Hamdi was assassinated in 1977, and his successor, former Chief of Staff Ahmed Hussein al-Ghashmi, was killed in June 1978. The lengthy tenure of President Ali Abdullah Saleh, who ruled North Yemen from 1978 until it merged with South Yemen in 1990, proved more stable. 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.