The size of these merchant caravans varied greatly depending on the state of trade and security. A "normal" size was around 1500 camels, though some reached as many as 4000. It was the "light caravans", however, that usually included the largest number of camels. In the seventeenth and eighteenth centuries, growing demand for camels throughout the Ottoman Empire, brought annual caravans of 3000 to 5000 unladen camels from Basra to Aleppo. In 1745, William Beawes estimated that around eleven thousand camels were sold in Aleppo, while Plaisted estimated the figure at 3000-4000 annually.135 The caravans originated from al-cUqayr and other parts of southern Arabia, and moved north picking up more camels around Zubara, Qatif and Kuwait. The various caravans assembled at the town of Zubayr, to the south-west of Basra, prior to departing for Aleppo. Ideally, The merchant caravans departed after the arrival of the Bengal ships, usually in July, while the light caravans normally left in April. This schedule, however, varied quite often due to the ever changing political, economic and security situation in Iraq leading William Beawes, who travelled with a merchant caravan in 1745, to remark:
...nor have the caravans such regard to the seasons of shipping as I imagined, being here informed their setting out is far from depending upon the will of the merchants but entirely upon the will of the Bashaw of Bagdat and the agreement of the principal tribes of Arabs.136
The normal route, some 780 miles, ran parallel to the Euphrates. The caravans rarely approached the river because the muddy surface slowed the camels down and the desert provided a haven from the numerous custom points. The caravan continued to grow as it approached Najaf and Karbala', and at Kubaysah it was usually joined by the Baghdad caravan. The entire trip took between 45 to 70 days for the large caravans, and some 25 days for the small ones.
Many merchants believed that Baghdad's control over Basra had a disruptive impact on the Aleppo caravan trade. As early as 1739, Baghdad's Wali, Ahmad Pasha, refused to allow caravans to go directly from Basra to Aleppo without first stopping at Baghdad to pay additional tolls.137 During the century the Basra-Aleppo route functioned best when Baghdad's control over Basra was weak. By the middle of the century, Basra's merchants seem to have reached an agreement with the Wali to pay the additional Baghdad customs at Basra, thus being spared the costly and time-consuming trip to Baghdad. Several caravans were allowed to proceed in this manner until the agreement was nullified due to problems in collection from Barsa.138 Prior to the Persian occupation, the struggle between Basra's merchants and the central government in Baghdad over the Aleppo trade intensified greatly. In 1774, the Wali refused a request from a number of merchants to organize a caravan to Aleppo thereby increasing secessionist tendencies in Basra.139 This conflict of interests had profound political implications which will be discussed later.
Toward the end of the century Aleppo faced a growing economic crisis.140 Among the numerous causes for this crisis were the civil war in Persia which affected Aleppo's silk trade, the increasing power of the Najdi tribes in the countryside, and the rise of Izmir and Damascus as Aleppo's primary rivals for the European and Middle Eastern trades respectively. Constantine Volney who visited Aleppo at the end of the century speaks of the utter devastation of the economy and the desolation of the city and its hinterland.141 This alone would have guaranteed a reduction in Basra's caravan trade, yet the situation became quite critical when the rising power of the Najdi tribes affected the security of the caravan route. The greatest damage was certainly done by the Wahhabis and their allies who succeeded in sacking Karbala' in 1802. Two years later they raided the southern suburbs of Basra causing much damage and lose of life.142
In addition to this, the Persian occupation of 1776-1779 had two immediate impacts on the Basra-Aleppo trade.143 First, it encouraged the development of a Kuwait-Aleppo route where Kuwait's relative isolation afforded it greater security and freedom of commerce. Secondly, the decline of the Basra-Aleppo trade gave a boost to the hitherto secondary Baghdad-Damascus trade. During the second half of the century Aleppo's trading position gradually gave way to the rise of Damascus as the primary commercial city of Syria.144 This combination of increasing controls from Baghdad, a decline in the security of the caravan route, the development of an alternative route from Kuwait, the wanning of Aleppo's commercial prominance and the rise of Damascus, all contributed to the decline of Basra's caravan trade at the end of the century.
Three primary conclusions emerge from our discussion of Basra's trade networks in the eighteenth century. First, it is clear that Basra acted as the link between the two regions of the Persian Gulf and Western India on the one hand, and Mesopotamia, Persia and Syria on the other. It is, therefore, quite natural that Basra's economy would react to any developments that might occur anywhere in these regions. Secondly, Basra's primary role in this trade was as a port-of-transit. Though Basra's dates were in demand, especially in India and the Persian Gulf, this alone did not justify the importance of the city in the trade networks of the region. More importantly was its strategic location linking the various routes between Europe, the Ottoman Empire, and India. Lastly, while all indications point to the decline of Basra's trade after the plague of 1773 and the Persian occupation of 1776-1779, these events represented only the short-term causes of this decline. More important were the significant structural transformations that affected the region after the rise of the Qajars in Persia, the decline of Aleppo, and the rising competitiveness of other ports in the Gulf. Likewise, the late eighteenth century witnessed the height of tribal power in southern Iraq enabling tribes, such as the Khazacil, cUbayd and Muntafiq to flout Baghdad's authority and disrupt the important trade routes with Baghdad and Aleppo. As late as 1850 Basra's Mutasallim, Macshuq Pasha, was still complaining of the government's inability to control the tribes and secure the chief inland trade routes.