They were challenged by the Zaidi Imam, Qasim the Great (r. 1597–1620), and by 1636, the Zaydi tribesmen had driven the Ottomans out of the country completely.

[4] The Ottomans had two fundamental interests to safeguard in Yemen: The Islamic holy cities of Mecca and Medina, and the trade route with India in spices and textiles—both threatened, and the latter virtually eclipsed, by the arrival of the Portuguese in the Indian Ocean and the Red Sea in the early 16th century.

[5] Hadım Suleiman Pasha, the Ottoman governor of Egypt, was ordered to command a fleet of 90 ships to conquer Yemen.

The country was in a state of incessant anarchy and discord as Pasha described it by saying:[6] Yemen is a land with no lord, an empty province.

It would be not only possible but easy to capture, and should it be captured, it would be master of the lands of India and send every year a great amount of gold and jewels to Constantinople.Imam al-Mutawakkil Yahya Sharaf ad-Din ruled over the northern highlands including Sana'a, while Aden was held by the last Tahiride Sultan 'Amir ibn Dauod.

Pasha stormed Aden in 1538, killing its ruler, and extended Ottoman authority to include Zabid in 1539 and eventually Tihama in its entirety.

[11] Indeed, Ottoman troops supported by tribal forces loyal to Imam al-Mutahhar stormed Taiz and marched north toward Sana'a in August 1547.

[13] Disregarding the delicate balance of power in Yemen by acting tactlessly, he alienated different groups within Yemeni society, causing them to forget their rivalries and unite against the Turks.

Imam al-Mutahhar launched a propaganda campaign in which he claimed that the Islamic prophet Muhammad came to him in a dream and advised him to wage jihad against the Ottomans.

The last decisive encounter took place in Dhamar around 1568, in which Murad Pasha was beheaded and his head sent to al-Mutahhar in Sana'a.

[16] Lala Kara Mustafa Pasha, the Ottoman governor of Syria, was ordered by Selim II to suppress the Yemeni rebels.

[22] After al-Mutahhar's demise in 1572, the Zaydi community was not united under an imam; the Turks took advantage of their disunity and conquered Sana'a, Sa'dah, and Najran in 1583.

He was succeeded by Al-Mutawakkil Isma'il, another son of al-Mansur al-Qasim, who conquered Yemen in its entirety, from Asir in the north to Dhofar in the east.

[36] The country established diplomatic relations with the Safavid dynasty of Persia, Ottomans of Hejaz, Mughal Empire in India, and Ethiopia, as well.

[38] The imamate did not follow a cohesive mechanism for succession, and family quarrels and tribal insubordination led to the political decline of the Qasimi dynasty in the 18th century.

The rising power of the fervently Islamist Wahhabi movement on the Arabian Peninsula cost the Zaidi state its coastal possessions after 1803.

The imam was able to regain them temporarily in 1818, but new intervention by the Ottoman viceroy of Egypt in 1833 again wrested the coast from the ruler in Sana'a.

[41] An incident played into British hands when, while passing Aden for trading purposes, one of their sailing ships sank and Arab tribesmen boarded it and plundered its contents.

The British India government dispatched a warship under the command of Captain Stafford Bettesworth Haines to demand compensation.

The ruler of Lahej, who was in Aden at the time, ordered his guards to defend the port, but they failed in the face of overwhelming military and naval power.

The British realised that Aden's prosperity depended on their relations with the neighbouring tribes, which required that they rest on a firm and satisfactory basis.

The Turks asserted to the British that they held sovereignty over the whole of Arabia, including Yemen as the successor of Mohammed and the Chief of the Universal Caliphate.

[41] Rivalries and disturbances continued among the Zaydi imams, between them and their deputies, with the ulema, with the heads of tribes, as well as with those who belonged to other sects.

Some citizens of Sana'a were desperate to return law and order to Yemen and asked the Ottoman Pasha in Tihama to pacify the country.

[49] In 1872, military forces were dispatched from Constantinople and moved beyond the Ottoman stronghold in the lowlands (Tihama) to conquer Sana'a.

[52] The tribal chiefs were difficult to appease and an endless cycle of violence curbed Ottoman efforts to pacify the land.

Ahmed Izzet Pasha proposed that the Ottoman army evacuate the highlands and confine itself to Tihama, and not unnecessarily burden itself with continuing military operation against the Zaydi tribes.