Dalmatia was a Roman province. Its name is probably derived from the name of an Illyrian tribe called the Dalmatae which lived in the central area of the eastern coast of the Adriatic Sea. It encompassed the northern part of Albania, Croatia, Bosnia and Herzegovina, Montenegro, Kosovo and Serbia, thus covering an area significantly larger than the current Croatian region of Dalmatia. Originally this region was called Illyria (in Greek) or Illyricum (in Latin). When it became one of the two parts of the Roman province of Illyricum it was renamed Dalmatia, tits counterpart province being Pannonia. Later the province of Illyricum was dissolved and replaced by two separate provinces: Dalmatia and Pannonia. It is not clear when this happened, but plausibly it occurred during the reign of the emperor Vespasian. The Croatian historian Aleksandar Stipčević writes that analysis of archaeological material from that period has shown that the process of romanization was rather selective. While urban centers, both coastal and inland, were almost completely romanized, the situation in the countryside was completely different. Despite the Illyrians being subject to a strong process of acculturation, they continued to speak their native language, worship their own gods and traditions, and follow their own social-political tribal organization which was adapted to Roman administration and political structure only in some necessities. In 454 Marcellinus, a military commander, rebelled against Valentinian III, the emperor of the west. He was in Dalmatia then. It is thought that he was the commander of the troops stationed there. He seized control of Dalmatia and governed it independently until his death in 468. Julius Nepos became the governor of Dalmatia even though he was a relative of the emperor of the east, Leo I the Thracian, and Dalmatia was under the western part of the Roman empire. Dalmatia remained an autonomous area. In 474 Leo I elevated Nepos as emperor of the western part of the empire in order to depose Glycerius, a usurper emperor. Nepos deposed the usurper, but was in turn deposed in 475 by Orestes, who made his son Romulus Augustus emperor in the west. Leo I refused to recognise him and still held Julius Nepos as the emperor of the west. Romulus Augustus was deposed in 476 by Odoacer, who proclaimed himself king of Italy. Nepos remained in Dalmatia and continued to govern it until he was assassinated in 480. Ovidia, a military commander, was in charge of Dalmatia for a few months. However, Odoacer used Nepos' murder as a pretext to invade Dalmatia, defeated Ovidia and annexed Dalmatia to his kingdom of Italy. In 488 Zeno, the new emperor of the east, sent Theodoric the Great, the king of the Ostrogoths to Italy. Zeno sent him to depose Odoacer. He also wanted to get rid of the Ostrogoths, who were Roman allies and were settled in the eastern part of the empire, but were becoming restless and difficult to manage. Theodoric fought a four-year war in Italy, killed Odoacer, settled his people in Italy and established the Ostrogothic Kingdom there. Dalmatia and the rest of the former diocese of Pannonia came under the Ostrogothic Kingdom.
The Theme of Dalmatia (thema Dalmatias/Delmatias) was a Byzantine theme (a military-civilian province) on the eastern coast of the Adriatic Sea in Southeastern Europe, headquartered at Jadera (Zara, now Zadar). Dalmatia first came under Byzantine control in the 530s, when the generals of Emperor Justinian I (r. 527–565) seized it from the Ostrogoths in the Gothic War. The invasions of the Avars and Slavs in the 7th century destroyed the main cities and overran much of the hinterland, with Byzantine control limited to the islands and certain new coastal cities -with local autonomy and called Dalmatian City-States- such as Spalatum and Ragusium, while Jadera became the local episcopal and administrative center, under an archon. These coastal cities were the refuge of the autochthonous Dalmatian neolatins, who created the original eight Dalmatian city-states (Vecla, Crespa, Arba, Jadera, Tragurium, Spalatum, Ragusium and Cattaro). At the turn of the 8th to 9th century, Dalmatia was seized by Charlemagne (r. 768–814), but he returned it to the Byzantines in 812, after the so-called "Pax Nicephori ". It is unclear whether the region was under actual rather than nominal Byzantine authority after that; the local Latin cities appear to have been virtually independent. Nevertheless, an archon of Dalmatia is mentioned in the 842/843 Taktikon Uspensky, and a seal of a "strategos of Dalmatia" dated to the first half of the century may indicate the existence of a Dalmatian theme. The traditional date of the establishment of Dalmatia as a regular theme is placed in the early years of the reign of Emperor Basil I the Macedonian (r. 867–886), following the expeditions of Niketas Oryphas. Byzantium, the Roman Pope and the Franks vied for the support of the Slavs in Dalmatia; in 878 AD, Zdeslav of Croatia was a noted Byzantine vassal, who deposed and was in turn deposed in a power struggle involving these powers. With the fall of the Carolingian Empire, the Franks ceased to be a major power in the Adriatic, while the Republic of Venice grew in power in Dalmatia, beginning with Doge Pietro Tradonico. Around 923 AD, Tomislav of Croatia, the Byzantine Emperor and the two church patriarchs were involved a deal that transferred the control of the Byzantine Dalmatian cities to the new Croatian kingdom. This started a series of similar maneuvers and the Croatian-Bulgarian Wars, during which the Byzantine Emperors of the Macedonian dynasty maintained varying degrees of control over the Dalmatian cities. The Church also endured an analogous internal conflict between the rival dioceses of Split and Nin. The Venetian maritime power was obstructed by the Narentines and the Croats until Pietro II Orseolo who successfully intervened in 998 and 1000, and arranged two important royal marriages with both the Croats and the Byzantines. Under Domenico I Contarini, Venice retook Jadera. Croatia had another brief period of control over the Dalmatian city-states under Peter Krešimir IV, but the invasion of the Normans shifted the balance of power back to the Venetians. Indeed, in 1075 AD the Norman Count Amico invaded Croatia from southern Italy, on behalf of the Dalmatian cities (by invitation to protect them from Croatian domination). Amico besieged Arbe for almost a month. He failed to take the island, but he allegedly did manage to capture the Croatian king himself (whose mother was the daughter of Doge Pietro Orseolo ) at an unidentified location. In return for liberation, he was forced to relinquish many cities, including both his Croatian capitals, as well as Zara, Spalatum, and Tragurium. However, over the next two years, the Venetians banished the Normans and secured the Dalmatian cities for themselves. In the south of the Dalmatia Theme, the city of Ragusa (Dubrovnik), one of the main Dalmatian city-states but still under Byzantine control, started to grow in importance, and its Church diocese was elevated to an archbishopric in 998 AD. In the early 11th century, Byzantine control over the eight Dalmatian city-states started to be contested by the Serbian principality of Duklja, whose ruler Jovan Vladimir took control of Bar, near the border with the Theme of Dyrrhachium. His feats were repeated and bested by Stefan Vojislav twenty years later, and in 1034 AD, the Bar diocese was elevated to an archdiocese, but a war with Theophilos Erotikos soon followed. Stefan Vojislav's son Mihailo obtained papal support following the East-West Schism of 1054, further weakening Byzantine influence in Dalmatia. Except for Ragusium and the southern third of Dalmatia, Byzantine control collapsed in the 1060s. Constantine Bodin pledged his support for Pope Urban II, which confirmed Bar's status as an archdiocese in 1089 AD, and resulted in a temporary demotion of the Ragusan diocese. By the end of the 11th century, the Kingdom of Hungary took the Kingdom of Croatia's place in controlling the northern Dalmatian hinterland. Duklja remained largely under Byzantine control, with a series of internal conflicts weakening its leaders. Byzantine predominance was restored under Emperor Manuel I Komnenos (r. 1143–1180), but vanished after his death and was replaced by Venetian control. With the rise of Stefan Nemanja, the Nemanjić dynasty took control of the lands in the south of coastal Dalmatia, while nearly all the Dalmatian islands and coastal north-central Dalmatia was under full Venetian control since the 13th century.
Dalmatian City-States were the Dalmatian localities where the local romance population survived the barbarian invasions. Eight little cities were created by those autochthonous inhabitants that maintained political links with the Byzantine Empire (that defended these cities allowing their commerce). The original name of the cities was Jadera, Spalatum, Crespa, Arba, Tragurium, Vecla, Ragusium and Cattarum. The language and the laws where initially Latin, but after a few centuries they developed their own neolatin language (the " Dalmatico"), that lasted until the 19th century. The cities were maritime centers with a huge commerce mainly with the Italian peninsula and with the growing Republic of Venice. Dalmatia after the fall of the Roman Empire consisted of a group of autochthonous coastal cities functioning much like city-states, with extensive autonomy, but in mutual conflict and without control of the rural hinterland controlled by the Slavs who arrived after 640 AD. Ethnically, Dalmatia started out as a Roman region, with a romance culture that began to develop independently, forming the now-extinct Dalmatian language called "Dalmatico". So, these cities were characterized by common Latin laws, catholic religion, the same romance language, common commerce and same political/administrative structures and entities. Since the seventh century there were eight areas of Byzantine Dalmatia that developed into eight "neo-latin" City-states, maintaining their Roman roots (language, ethnic population, customs, laws, etc..) despite the destructive barbarian invasions. Indeed, in the Early Medieval period, Byzantine Dalmatia was ravaged by an Avar invasion that destroyed its capital, Salona, in 639 AD, an event that allowed for the settlement of the nearby Diocletian's Palace in Spalatum by Salonitans, greatly increasing the importance of the city. The Avars were followed by the great South Slavic migrations. The Slavs, loosely allied with the Avars, permanently settled the region in the first half of the 7th century AD and remained its predominant ethnic group ever since. The Croats soon formed their own realm: the Principality of Dalmatian Croatia ruled by native Princes of Guduscan origin. The meaning of the geographical term "Dalmatia", now shrunk to the cities and their immediate hinterland. These cities and towns remained influential as they were well fortified and maintained their connection with the Byzantine Empire. The two communities were somewhat hostile at first, but as the Croats became Christianized this tension increasingly subsided. A degree of cultural mingling soon took place, in some enclaves stronger, in others weaker, as Slavic influence and culture was more accentuated in Ragusium and Cattarum while the influence from the Italian peninsula was stronger in the northern Dalmatia islands and in Jadera and Spalatum. Around 950 AD as the Dalmatian city states gradually lost all protection by Byzantium, being unable to unite in a defensive league hindered by their internal dissensions, they had to turn to Venice for support. Each of the Dalmatian city states needed protection (even from Narentane piracy), based mostly on economic reasons. In the year 1000 AD an expedition of Venetian ships in coastal Istria and Dalmatia secured the Venetian suzerainty in the area, and the Narentines, Slav pirates, were suppressed permanently. In the occasion Doge Orseolo named himself "Duke of Dalmatia", starting the colonial Empire of Venice. The Venetians, to whom the Dalmatians were already bound by language and culture, could afford to concede liberal terms as its main goal was to prevent the development of any dangerous political or commercial competitor on the eastern Adriatic. The seafaring community in Dalmatia looked to Venice as the new "queen" of the Adriatic sea. In return for protection, these 8 "neolatin" cities often furnished a contingent to the army or navy of their suzerain, and sometimes paid tribute either in money or in kind. Arbe (actual Rab), for example, annually paid ten pounds of silk or five pounds of gold to Venice. The Dalmatian cities might elect their own chief magistrate, bishop and judges; their Roman law remained valid and they were even permitted to conclude separate alliances. In these centuries started to disappear the Dalmatian language, that was assimilated by the venetian dialect.Dalmatian was spoken on the Dalmatian coast from Fiume (Rijeka) as far south as Cottorum (Kotor) in Montenegro. Speakers lived mainly in the coastal towns of Jadera (Zadar), Tragurium (Trogir), Spalatum (Split), Ragusium (Dubrovnik) and also on the islands of Curicta (Krk), Crepsa (Cres) and Arba (Rab). Almost every city developed its own dialect, but the most important dialects we know of were Vegliot, a northern dialect spoken on the island of Curicta, and Ragusan, a southern dialect spoken in and around Ragusa (Dubrovnik). The cities of Jadera, Spalatum, Tragurium and Ragusium and the surrounding territories each changed hands several times between Venice, Hungary and the Byzantium during the 12th century. In 1202, the armies of the Fourth Crusade rendered assistance to Venice by occupying Jadera, that started to be officially called Zara. In 1204 the same army conquered Byzantium and finally eliminated the Eastern Empire from the list of contenders on Dalmatian territory. The late 13th century was marked by a decline in external hostilities. The Dalmatian cities started accepting complete foreign sovereignty, mainly the one of the Republic of Venice. The only exception was Ragusium, that remained independent creating the Republic of Ragusa that lasted until the 1807 Napoleon conquest.