For about 900 years frequent pirate invasions were the main characteristic in the history of the island. They were in full swing in the Aegean Sea particularly in the 7th century and afterwards. Saracens, Arabs and Slavs have left their marks on the island (as many place-names by the sea show) and doomed it to introversion and oblivion.
The only inhabited part of the island that could be seen from the sea at that time was the rock of (nowadays called) Ano Syra very close to the ancient densely populated town. The establishment of this naturally protected settlement of the people of Syros hunted by the invaders, is thought likely to have taken place in the early 9th century AD. Being part of the Byzantine Aegean Sea dominions, Syros was under the rule of the Diosece of Delos, then that of Athens and finally that of Kea – Thermia – Serifos.
After the fall of the Byzantine to the Francs, Syros is subjected to the Venetian rule and is included together with most of the Cycladic islands in the Dutchy of the Aegean Sea, in 1207.
The Venetians attempted to impose feudal administrative and financial system but to no avail. At the same time Catholicism was established and officially recognised by the residents while both the Greek language and the Greek customs remained equally alive and unchanged. Numerous place-names, the preservation of Orthodox worship ceremonies, the Eastern church calendar as well as a great number of historical sources of the era written almost exclusively in Greek are representatives of national identity preservation.
The Venetian domination was marked by constant strife between various Frank rulers on the domination of the islands. Typical of this was the siege of Syros by the Duke of Tinos, Bartholomew Gizis, in 1286. The pirate invasions that ensued in all the Aegean Sea affected Syros too although the island was under the protection of the Western powers and the Roman Catholic Church in particular. During all this time Syros was part of the Dutchy of the Aegean Sea, but with its own governor mainly assigned to collect taxes. The Catholic clergy was politically and financially powerful on the island.
The Turkish domination in the Aegean Sea grew constantly and in the mid-16th century in the Cyclades the Turkish – Venetian clashes turn on the Turkish side. In 1537 Syros is seized by the Turks. The Turkish rule was limited to tax paying while local government started to develop.
The residents (approximately 300 then) suffered constant raids by Frank pirates, who were in conflict with the Turks. Quite often the locals were compromised by such conflicts with the hottest part being the beheading of the (Catholic) bishop of Syros Andreas Kargas by Captain Ali Passas in October 1617. The pasha considered the islanders under their bishop’s commands as plotters against the Turkish domination.
Meanwhile, the pirate raids had resulted in the depopulation of many Aegean Sea islands. This is also certified in a 1563 Venetian report, according to which out of 16 islands of the Dutchy of the Aegean Sea only 5 were still inhabited with Syros being one of them. The population number reached a new low after the 1617 calamity as it is shown in Catholic Bishop Marengo’s report on 27 June 1626. The two Turkish – Venetian Wars that ensued caused new sufferings to the island.
In 1633 Capuchin monks establish in Syros. Towards the end of the 17th century, both the administration (local decisions, taxation, etc.) and the juridical decisions became favourable to Syros. Local administration was enacted: the people’s assembly, the delegates and the elders. All men over 30 participated in the first. The assembly gradually attained the power to legislate. The delegates were elected by the assembly for one year with administration power, the mere ratification of which was by the Sublime Porte. The elders were old delegates, also elected by the assembly, who contributed to the local administration and juridical decisions.
In 1680 the Community of Syros exempted from all taxes the port of the island and this way the basis for trade development was laid. The island was under the jurisdiction of the Turk Chief Justice residing in Andros. There were no Turks on the island and the bishop was appointed by the Pope. A growing French influence contributed towards the above development since France had got a number of privileges on behalf of the local clergy from the Turks. Signs of security as well as financial development for the residents resulted in a growth in population and in the second half of the 18th century more than 2.500 people inhabited the island (according to the testimony of a local abbot Della Roca), all of them Catholics except for a few Orthodox families. The island started being intensively cultivated. Young people were sent to Italian universities to become educated under the auspices of the Pope. That progress was cut short by a cholera epidemic in 1728.
During the Russian – Turkish war (in 1771 all the Cyclades were seized by the Russian fleet) Syros was ruled by three commanders with emergency powers. At that time taxation was dual (in money and goods). Meanwhile a great number of local antiquities were pillaged with the active participation of the Russian admiral.
After the islands were recaptured by Captain Pasha, reprisal was avoided due to the positive contribution of Stephanos Mavrogenous, a pasha interpreter from Paros (later ruler of Wallachia). Syros between 1779 and 1803 was subjected directly to the Sultan’s niece who instituted reduction in taxes and encouraged local institutions (elders, etc.).
In 1814, the privilege of the appointment of moneyed people in key power positions was called off after a popular uprising and lower class representatives were appointed instead in local administration.
The sea routes in the Eastern Mediterranean were safe again circa 1800 and afterwards after the decline of the piracy and the entailing dangers in the Aegean Sea. Consequently, Syros having a key geographical position, the constant support of the western powers and self-rule develops rapidly into a maritime centre and its port is revived. At that point the Greek War of Independence starts.