The Sasanian naval forces were established since the time of the empire's founder, Ardashir I. The main role of the Sasanian navy was to protect Sasanian economic interests, not military expeditions, as the coasts of the Persian Gulf were already under rule of Sasanians or their vassals. According to V. A. Dmitriev, the role of the navy was to enhance the military, political, and commercial influence of the empire in the north of the Indian Ocean. The navy was mostly active in the Persian Gulf, the Red Sea, and the Arabian Sea. The Sasanians did not emphasize the development of their navy due to their geopolitical interests as well as the fact that their military was highly influenced by the land-based military of the Parthian Empire, and that, unlike the Achaemenids, the Sasanians failed to capture the ports of the Eastern Mediterranean. The leader of the navy allegedly bore the title of navbed.
Vessels
The vessels used by the Sasanian military were exclusively transport landing ships used to transport land forces, and possibly also merchant ships to transport cavalry. The dhow-type vessels were used in the Indian Ocean basin, while the Byzantine-style sailing-rowing dromons and chelandions were used in the Mediterranean, but only for the purpose of transporting troops. The Persians were able to construct large ships suited for long voyages as far as the marginal seas of the north of the Indian and west of the Pacific Oceans.
Operational history
There were two distinct areas of operation for the Sasanian navy: the Indian Ocean basin and the Mediterranean. Sasanian navy played an important role in Ardashir I's conquest of the Arabian side of the Persian Gulf as well as in Shapur II's Arab campaign. The peak of the navy's activities was during the reign of Khosrow I, who sent a force of eight ships under Vahrez to conquer Yemen—each ship could carry 100 men. Six of the ships managed to reach Yemen safely. An attempt by Khosrow I to establish a Sasanian fleet in the Black Sea via the ports of Lazica in 540s, which was able to directly threaten the heart of the Byzantine Empire, was thwarted by the defeats at Petra and Phasis in the last stage of the Lazic War. During the climactic Byzantine–Sasanian War of 602–628, the Sasanian navy tried naval expeditions in the Mediterranean Sea—although not very successful, they managed to capture the island of Rhodes in 622/3 and several other islands in the eastern Aegean around the same time. Since the Sasanians did not use to have a fleet in the Mediterranean, it has been suggested that their forces were transported either by the captured Byzantine ships in the newly conquered ports or by vessels built in Egyptian or Syrian shipyards especially for them. Later in that war, they were forced to rely on monoxyla of their allied Slavs in order to transport the 3,000 troops across the Bosphorus which they had promised the khagan of the Avars. The weakness of the Sasanian navy is considered a key factor in their failure to defeat the Byzantines in the last war between them. After the Muslim conquest of Persia, the Sasanian navy forces joined the Muslim armies and participated in the wars against the Byzantines and elsewhere. For example, according to the Chinese source Old Book of Tang, Guangzhou was ravaged and burned during the joint naval expedition of the Arabs and the Persians in 758.
