The trade route through the Persian Gulf had to first run through Strait of Hormuz before reaching the Arabian Sea and continuing through the middle route to Asia. Here, a number of principalities and smaller cities took advantage of their location and began to impose their influence on merchant vessels. These people either imposed a toll of tribute on merchant vessels trying to pass through to the ports which connected to land routes or captured their own sections of the trade, pushing their status as small city-states to commercial centers along the trade route. Merchants traveling to and from Baghdad, India, and China, along with from the Red Sea route would dock at these centers and exchange goods creating a new market which previously did not exist, helping economy systems of these port cities to prosper.
Something I found interesting was how that even with the dominance of Baghdad declining, commerce between the Gulf region and China remained prosperous. Merchants were still raking in huge fortunes through this route. What spawned from this power shift was the emergence of independent entrepreneurs who competed with each other for control over trade throughout the Gulf, weather it was through legitimate business or piracy. One example is the island of Qais, which practiced both. It began with the use of blockades on major trade passages through the first half of the twelfth century to acquire goods from passing merchants. Then during the Mongol conquest of Persia and Iraq in the late thirteenth century, this port became a key center of trade for the Asian market.
I wonder if the piracy practiced by the people of the island of Qais was so significant in their development into one of the key ports along the middle route. Would their fate have been the same if say they concentrated on becoming a legitimate center from the start?