Imam Radi Abdullah had dispatched his da’is in all directions, the most acclaimed among them was Ibn Hawshab. When the Imam found that Ibn Hawshab was groomed enough for the responsibility of its promulgation, he jointly entrusted him and his colleague, Ibn Fazal, with the task of Ismaili mission in Yamen. They conquered Sana’a, the capital of Yamen, and exiled the ruling tribe of Banu Laydir, and established Ismaili authority in Yamen. The Ismaili mission reached the apex of its influence in Yamen, from where Ibn Hawshab dispatched many da’is to the farthest corners. Thus, Yamen became a vital zone and an important hub of Ismaili dawa.
In 291/904, a close associate of Ibn Hawshab, called Ali bin Fazal al-Jadani had shown signs of disloyalty, and in 299/911, he publicly renounced his allegiance to Imam al-Mahdi. It must be noted that in Egypt, when Imam al-Mahdi decided to go to Maghrib instead of Yamen in 291/904, the da’i Firuz also gave up Ismaili faith and fled to Yamen, and instigated a revolt. He won the support of Ali bin Fazal. Subsequently, Firuz was killed and Ali bin Fazal endeavoured unsuccessfully to coerce the collaboration of Ibn Hawshab. The death of Ibn Hawshab took place in 303/914, and made a will to his son Abul Hasan Mansur and his pupil Abdullah bin Abbas al-Shawiri to administer the mission in Yamen till an official appointment of a new chief da’i. Upon his death, al-Shawiri sent a letter to Imam al-Mahdi, reporting the death of Ibn Hawshab, and requesting for any chief da’i instead. In a reply, the Imam confirmed the post of al-Shawiri as a chief da’i. Jafar, the son of Ibn Hawshab was alone among his brothers to demonstrate his loyalty to the Fatimids, but his elder brother, Abul Hasan Mansur, who was expecting to succeed his father, had defected from the mission, and returned to his castles in Miswar, where his brothers joined him. Jafar, noticing the inimical intentions of his brothers towards al-Shawiri, tried to persuade that a quarrel would only lead to impair the Ismaili influence in Yamen. In spite of this warning, Abul Hasan Mansur waited for his opportunity, and killed al-Shawiri and took the dominions. Jafar immediately went to Maghrib, where he reached when Imam al-Mahdi had expired in 322/934. Imam al-Qaim charged him the mission work in Maghrib, where he also served Imam al-Mansur and Imam al-Muizz, and was commonly known as Jafar bin Mansur al-Yamen.
During the period of Imam az-Zahir, the headship of the Yamenite mission had come to be vested in a certain da’i Suleman bin Abdullah al-Zawahi. He made a large conversion and wished to re-establish the political power of the Ismailis. It is said that a certain Hamdani chieftain, named Ali bin Muhammad al-Sulayhi, the son of the qadi of Haraz, once came to lead the pilgrim caravans to Mecca, and had learnt much about Ismaili doctrines from Suleman and espoused Ismailism. Ali took a leading part in the mission works in Yamen and became the assistant of Suleman, who chose him as his successor. Ali bin Muhammad al-Sulayhi generated his close contact with Imam az-Zahir.
In 429/1038, during the period of Imam al-Mustansir billah, Ali bin Muhammad captured Mount Masar in Haraz to the north of Yamen, and fortified it, whom he made his centre. This marked the foundation of the Sulayhid dynasty, which ruled over Yamen as a vassal of the Fatimids for almost a century until 532/1138. He obtained support from the Hamdani, Humayri and other petty tribes of Yamen and instituted the Fatimid khutba everywhere.
In 450/1058, Ali bin Muhammad al-Sulayhi succeeded to expel the Zaidis from San’a, and made it his capital. In 452/1060, he captured Zabid after killing Sa’d bin Najah, the founder of the Najahid dynasty and appointed his brother-in-law, Asad bin Shihab as the governor of Zabid. In 454/1062, he conquered Adan, where he allowed Banu Ma’n to rule for sometime as tributaries of the Sulayhids. Later, in 476/1083, the Sulayhids granted the governorship of Adan to two Hamdani brothers, Abbas and Masud bin Karam, who founded the Ismaili dynasty of the Zurayids in Adnan from 476/1083 to 569/1173. In sum, Ali bin Muhammad subjugated all of Yamen in 455/1063 and also extended his influence from Mecca to Hazarmaut.
Ali bin Muhammad set out on a pilgrimage to Mecca in 459/1067 at the head of 2000 horsemen of whom 160 were the members of his household. Unfortunately, he was killed with a number of his relatives in a surprise attack by the sons of Sa’d bin Najah in reprisal of his father’s death. His son Ahmad al-Mukarram was declared the head of Yamen by Imam al-Mustansir. The rule which Ali bin Muhammad al-Sulayhi founded would have fallen to the ground if his son Ahmad al-Mukarram had not come to its rescue and restored it.
Ahmad al-Mukarram died in 484/1091 and his wife Sayyida Hurrat al-Malika Arwa (477-532/1084-1138) then began to govern on behalf of Mukarram’s minor son, Ali Abd al-Mustansir. When he too died, Sayyida Arwa took up the reins of administration of the state and mission, and remained loyal to Imam al-Mustansir. She however supported the Mustalian line after the death of Imam al-Mustansir, and since then, there were no missionary activities of the Nizari Ismailis in Yamen.
Mrs. Shirin Keshani, who delegated from Aden to the World Ismailia Socio-Economic Conference in Karachi on December 15, 1964 have furnished some valuable details during her paper reading. She had migrated to Aden in 1940 with her husband, Dr. Ghulam Hussain V. Keshani, where they found only forty Ismailis. In 1947, Count Abdullah Hashim Gangaji arrived in Aden on a business trip and learnt the problems of the Ismailis. In 1953, Shirin Keshani attended the Coronation of Queen Elizabeth in London as a representative of Aden, and had a chance to see Imam Sultan Muhammad Shah and sought a permission to open a jamatkhana in Aden. She procured a piece of land, but the Arabs opposed. Her husband was a medical practitioner and treating the governor, therefore, she succeeded. In 1954, a delegation of the Imam arrived in Aden with Count Abdullah, Count Hasan Lakha and Count Nazar Ali. They opened a temporary jamatkhana in the house of Hasan Ali Pir Muhammad, where the Ismailis offered their prayers for two years till the new was constructed. The governor of Aden laid the foundation stone of the new jamatkhana in 1956. Dewan Sir Eboo Pirbhai also attended. In 1957, the Imam visited Aden when the construction was in progress. Finally, it became ready in 1958 and was opened by Dr. Keshani, who was also the first President of the Ismaili Council for Aden, which was joined with the Mombasa Council. At that time the number of the Ismailis was 95 to 100.