To secure Egypt's external trade, they tried to keep all naval routes to Egypt under their control.
The Ptolemies also traded with Egypt's colonies and other foreign countries. The early Ptolemies were successful to the extent that they maintained political and economic dominance over the Aegean Sea, making Alexandria one of the foremost commercial centers of the world.
The fact that Alexandria contained two ports, both of which were developed by the Ptolemies, was a further asset. Some of Egypt's imports, and the majority of Egypt's exports passed through it.
Alexandria was also at the intersection of trade routes and had a huge amount of imports and exports passing through it.
During the Roman era, the emperors paid great attention to external trade. Thus, external trade flourished, especially after they rid the Mediterranean Sea of pirates. Roman control spread to the shores of the Red Sea and Egypt monopolized certain industries such as glass, paper, and glass cubes.