Corfu, the first of the Ionian Islands encountered at the entrance to the Adriatic, was annexed to Greece by a group of Eretrians (775-750 BCE). In 734 BCE the Corinthians founded a colony known as Kerkyra to the south of where the Old Town now stands. The town became a trading post on the way to Sicily and founded further colonies in Illyria and Epirus. The coast of Epirus and Corfu itself came under the sway of the Roman Republic (229 BCE) and served as the jumping-off point for Rome's expansion into the east. In the reign of Caligula two disciples of the Apostle Paul, St Jason, Bishop of Iconium, and Sosipater, Bishop of Tarsus, introduced Christianity to the island.
Corfu fell to the lot of the Eastern Empire at the time of the division in 336 and entered a long period of unsettled fortunes, beginning with the invasion of the Goths (551).
The population gradually abandoned the old town and moved to the peninsula surmounted by two peaks (the korifi) where the ancient citadel now stands. The Venetians, who were beginning to play a more decisive role in the southern Adriatic, came to the aid of a failing Byzantium, thereby conveniently defending their own trade with Constantinople against the Norman prince Robert Guiscard. Corfu was taken by the Normans in 1081 and returned to the Byzantine Empire in 1084.
Following the Fourth Crusade and the sack of Constantinople by the Crusaders in 1204, the Byzantine Empire was broken up and, in return for their military support, the Venetians obtained all the naval bases they needed to control the Aegean and the Ionian Seas, including Corfu, which they occupied briefly from 1204 to 1214. For the next half-century, the island fell under the sway of the Despots of Epirus (1214-67) and then that of the Angevins of Naples (1267-1368), who used it to further their policies against both the Byzantine Empire now re-established in Constantinople and the Republic of Venice. The tiny medieval town grew up between the two fortified peaks, the Byzantine Castel da Mare and the Angevin Castel di Terra, in the shelter of a defensive wall fortified with towers. Writings from the first half of the 13th century tell of a separation of administrative and religious powers between the inhabitants of the citadel and those of the outlying parts of the town occupying what is now the Spianada.
In order to assert its naval and commercial power in the Southern Adriatic, the Republic of Venice took advantage of the internal conflicts raging in the Kingdom of Naples to take control of Corfu (1386-1797). Alongside Negropont (Chalcis), Crete, and Modon (Methoni), it would form one of the bases from which to counter the Ottoman maritime offensive and serve as a revictualling station for ships en route to Romania and the Black Sea.
The ongoing work on defining, improving, and expanding the medieval fortified perimeter reflects the economic and strategic role of Corfu during the four centuries of Venetian occupation. In the early 15th century activity concentrated on the medieval town, with the development of harbour facilities (docks, quays and arsenals) and continued with the renovation of the defence works. Early in the following century a canal was dug, cutting off the medieval town from its suburbs.
Following the siege of the town by the Turks in 1537 and the burning of the suburbs, a new programme of works was launched to isolate the citadel further and strengthen its defences. The strip of land (now the Spianada) cleared in 1516 was widened by demolishing houses facing the citadel walls, two new bastions were raised on the banks of the canal, the elevation of the perimeter walls was lowered, and the two castelli were replaced by new structures. The work, based on plans drawn by Veronese architect Michele Sanmicheli (1487-1559), were completed in 1558, bringing the town's defences up to date with the rapid progress made in artillery in recent decades.
Yet another siege by the Turks in 1571 decided the Venetians to embark on a vast project covering the medieval town, its suburbs, the harbour, and all the military buildings (1576-88). Ferrante Vitelli, architect to the Duke of Savoy, sited a fort (the New Fort) on the low hill of St Mark to the west of the old town to command the surrounding land and at sea, and also the 24 suburbs enclosed by a ditched wall with bastions and four gates. More buildings, both military and civil, were erected and the 15th century Mandraki harbour was restructured and enlarged. At the same time, the medieval town was converted to more specifically military uses (the cathedral was transferred to the new town in the 17th century) to become the Old Citadel.
Between 1669 and 1682 the system of defences was further strengthened to the west by a second wall, the work of military engineer Filippo Vernada. In 1714 the Turks sought to reconquer Morea (the Peloponnese) but Venetian resistance hardened when the Turkish forces headed towards Corfu. The support of Christian naval fleets and an Austrian victory in Hungary in 1716 helped to save the town. The commander of the Venetian forces on Corfu, Giovanni Maria von Schulenburg, was inspired by the designs of Filippo Vernada to put the final touches to this great fortified ensemble. The outer western defences were reinforced by a complex system of outworks on the heights of two mountains, Abraham and Salvatore, and on the intermediate fort of San Rocco (1717-30).
The treaty of Campo Formio (1797) marked the end of the Republic of Venice and saw Corfu come under French control (1797-99) until France withdrew before the Russian-Turkish alliance that founded the State of the Ionian Islands, of which Corfu would become the capital (1799-1807). The redrawing of territorial boundaries in Europe after the fall of Napoleon made Corfu, after a brief interlude of renewed French control (1807-14), a British protectorate for the next half-century (1814-64).
As the capital of the United States of the Ionian Islands, Corfu lost its strategic importance. Under the governance of the British High Commissioner Sir Thomas Maitland (1816-24), development activity concentrated on the Spianada; his successor, Sir Frederic Adam (1824-32), turned his attention towards public works (building an aqueduct, restructuring the Old Citadel and adding new military buildings at the expense of the Venetian buildings, reconstruction and raising of the town's dwellings) and the reorganisation of the educational system (the new Ionian Academy was opened in 1824), contributing to the upsurge in intellectual interests sparked during the French occupation. At the same time, the British began demolishing the outer fortifications on the western edge of the town and planning residential areas outside the defensive walls.
In 1864 the island was attached to the Kingdom of the Hellenes. The fortresses were disarmed and several sections of the perimeter wall and the defences were gradually demolished. The island became a favoured holiday destination for the aristocracy of Europe. The Old Town was badly damaged by bombing in 1943. Added to the loss of life was the destruction of many houses and public buildings (the Ionian Parliament, the theatre, and the library), fourteen churches, and a number of buildings in the Old Citadel. In recent decades the gradual growth of the new town has accelerated with the expansion of tourism.