attacked the town. He held out for nine months, finally forcing the Persian commander of Nader Shah's army to come to terms and leave the country altogether within a few years. He was elected imam in 1744, marking the last time Oman was occupied by foreign parties and the beginning of a new unified state. It was also the start of a dynasty that has lasted to the present day, making it one of the oldest surviving royal dynasties in Arabia and the first to gain independence. His descendants did not take the religious title of Imam, but Sayyid, an honorific title held by members of the royal family to this day, thus relinquishing all pretense of spiritual authority while fostering Muslim scholars and promoting Islamic scholarship. Trade flourished during Ahmed's thirty-nine-year reign and the Omani navy developed into a formidable force in the Indian Ocean second only to Great Britain and capable of purging Persians forces from the entire region and protecting Ottoman vessels in the Gulf of Oman, Indian Ocean and the Pirate Coast of Trucial Oman. Sultan bin Ahmed strengthened the already powerful fleet by adding numerous gunships and sleek cargo vessels. He also needed a strong ally to help him regain control of Mombasa from the Mazrui clan, fight off the movement spreading from what is now Saudi Arabia and to keep the Qasimi tribes from the Persian city of Lingeh out of Oman. He found this able ally in Great Britain, who by this time was a powerful maritime nation with an empire expanding all over the world. In the late 18th century, the second British Empire was at war with France and knew that the French emperor, Napoleon Bonaparte, was planning to march through Persia and capture Muscat on his way to invade India. In 1798 Britain and Oman agreed a Treaty of Commerce and Navigation. Sultan bin Ahmed pledged himself to British interests in India, and his territories became out of bounds to the French. He allowed the British East India Company to establish the first trading station in the Persian Gulf, and a British consul was posted to Muscat. During the reign of the renowned Sultan Said bin Sultan, the progenitor of the Busaidi dynasty, he took Oman to its zenith as a commercial and political maritime power: extending its borders to include Mombasa and parts of the east African coast, Zanzibar, Pemba Island, Mafia Island, Lamu Archipelago, Cape Delgado (northern border of the current Mozambique), Bandar-Abbas and the southern Iranian coast, Gwadar province of Balochistan and, for a short time Bahrain. He was counted among the best leaders as his reputation spread to the crown heads of Europe and became known as Said the Great. Few Arab leaders of any time were as well known and respected as Sheikh Said. Trade flourished and Muscat became a key market for the Persian Gulf.