It can be confusing that the geographical name "Dacia" was much later also used during the Middle Ages by the Roman Catholic Church for its northernmost province, namely Denmark-Norway-Sweden (Scandinavia) and even for Denmark alone. In some historical documents, members of royalty of that area have been called "of Dacia".
Towards the west Dacia may originally have extended as far as the Danube, where it runs from north to south at Waitzen (Vác). Julius Caesar in his De Bello Gallico (book 6) speaks of the Hercynian forest extending along the Danube to the territory of the Dacians. Ptolemy puts the eastern boundary of Dacia Trajana as far back as the Hierasus (Siret river, in modern Romania).
The extent and location of the later geographical entity Dacia varied in its four distinct historical periods (see History, below);
Based on archaeological findings, the origins of the Dacian culture can be considered to have begun developing from north of the Danube river (south and east) to the Carpathian mountains, in the modern-day historical Romanian province of Muntenia and are identified as an evolution of the Iron Age Basarabi culture.
The Dacians had attained a considerable degree of civilization by the time they first became known to the Romans.
According to Herodotus History (book 4) account of the story of Zalmoxis (or Zamolxis), the Getae (speaking the same language as the Dacians - Strabo) believed in the immortality of the soul, and regarded death as merely a change of country. Their chief priest held a prominent position as the representative of the supreme deity, Zalmoxis. The chief priest was also the king's chief adviser. The Goth Jordanes in his Getica (The origin and deeds of the Goths), gives account of Dicineus (Deceneus), the highest priest of Buruista (Burebista) and considered the Dacians a related nation of the Goths.
Besides Zalmoxis, the Dacians believed in other deities such as Gebeleizis and Bendis.
Dacians were divided into two classes: the aristocracy (tarabostes) and the common people (comati). The aristocracy alone had the right to cover their heads and wore a felt hat (hence pileati, their Latin name). The second class, who comprised the rank and file of the army, the peasants and artisans, might have been called capillati (in Latin). Their appearance and clothing can be seen on Trajan's Column.
Dacians had developed the Murus dacicus, characteristic to their complexes of fortified cities, like their capital Sarmizegetusa in today Hunedoara County, Romania. The degree of their urban development can be seen on Trajan's Column and in the account of how Sarmizegetusa was defeated by the Romans. The Romans identified and destroyed the water aqueducts or pipelines of the Dacian capital, only thus being able to end the long siege of Sarmizegetusa.
Greek and Roman chroniclers record the defeat and capture of Lysimachus in the 3rd century BC by the Getae (Dacians) ruled by Dromihete, their military strategy, and the release of Lysimachus following a debate in the assembly of the Getae.
The cities of the Dacians were known as -dava, -deva, -δαυα ("-dawa" or "-dava", Anc. Gk.), -δεβα ("-deva", Byz. Gk.) or -δαβα ("-dava", Byz. Gk.), etc. . A list of Dacian davas 1 and, more actual, at SOLTDM:
Gil-doba, a village in Thracia, of unknown location.
Thermi-daua, a town in Dalmatia. Probably a Grecized form of *Germidava.
The chief occupations of Dacians were agriculture, apiculture, viticulture, livestock, ceramics and metal working. The Roman province Dacia is represented on Roman Sestertius (coin) as a woman seated on a rock, holding aquila, a small child on her knee holding ears of grain, and a small child seated before her holding grapes.
They also worked the gold and silver mines of Transylvania. They carried on a considerable outside trade, as is shown by the number of foreign coins found in the country (see also Decebalus Treasure).
Commercial relations were flourishing for centuries, first with the Greeks, then with Romans, as we can find even today an impressive collection of gold currency used in various periods of Dacian history. The first coins produced by the Geto-Dacians were imitations of silver coins of the Macedonian kings Philip II and Alexander III (the Great). Early in the 1st century BC, the Dacians replaced these with silver denarii of the Roman Republic, both official coins of Rome exported to Dacia and locally made imitations of them.
The Dacians spoke an Indo-European language, but its characteristics are still disputed, due to insufficient archaeological evidence. Greek sources quote some place names, words, and even a list of about fifty plants written in Greek and Roman sources (see List of Dacian plant names), but this is still not enough to classify it, although many scholars assume it was part of the Satem branch.
The migrations of the fore bearers of Ancient Greece (ca. 750 BC— or earlier) most likely originated at least in part from periodic swelled populations in the easy living found in the fertile plains of the region. Such migrations were in mythological times, and well before historical records. It is likely that trade with communities along the Danube via the Black sea was a regular occurrence, even in Minoan times (2700 to 1450 BC).
At the beginning of the 2nd century BC, under the rule of Rubobostes, a Dacian king in present-day Transylvania, the Dacians' power in the Carpathian basin increased by defeating the Celts who previously held the power in the region.
A kingdom of Dacia was in existence at least as early as the first half of the 2nd century BC under King Oroles. Conflicts with the Bastarnae and the Romans (112 BC-109 BC, 74 BC), against whom they had assisted the Scordisci and Dardani, greatly weakened the resources of the Dacians.
Under Burebista (Boerebista), a contemporary of Julius Caesar, who thoroughly reorganised the army and raised the moral standard of the people, the limits of the kingdom were extended to their maximum. The Bastarnae and Boii were conquered, and even the Greek towns of Olbia and Apollonia on the Black Sea (Pontus Euxinus) recognised Burebista's authority.
Indeed the Dacians appeared so formidable that Caesar contemplated an expedition against them; something his death prevented. About the same time, Burebista was murdered, and the kingdom was divided into four (or five) parts under separate rulers. One of these was Cotiso, whose daughter Augustus is said to have desired to marry and to whom Augustus betrothed his own five-year-old daughter Julia. He is well known from the line in Horace (Occidit Daci Cotisonis agmen, Odes, III. 8. 18).
The Dacians are often mentioned under Augustus, according to whom they were compelled to recognise Roman supremacy. However they were by no means subdued, and in later times to maintain their independence they seized every opportunity of crossing the frozen Danube during the winter and ravaging the Roman cities in the province of Moesia.
Trajan turned his attention to Dacia, an area north of Macedon and Greece and east of the Danube that had been on the Roman agenda since before the days of Caesar when they had beaten a Roman army at the Battle of Histria. In 85, the Dacians had swarmed over the Danube and pillaged Moesia and initially defeated an army the Emperor Domitian sent against them, but the Romans were victorious in the Battle of Tapae in 88 AD and a truce was drawn up.
From AD85 to AD89, the Dacians (under Decebalus) were engaged in two wars with the Romans.
In AD87, the Roman troops under Cornelius Fuscus were defeated, and Cornelius Fuscus was killed by the Dacians under the authority of their ruler, Diurpaneus. After this victory, Diurpaneus took the name of Decebalus. The next year, AD88, new Roman troops under Tettius Iullianus, gained a signal advantage, but were obliged to make peace owing to the defeat of Domitian by the Marcomanni, so the Dacians were really left independent. Even more, Decebalus received the status of "king client to Rome", receiving from Rome military instructors, craftsmen and even money.
Emperor Trajan recommenced hostilities against Dacia and, following an uncertain number of battles, defeated the Dacian general Decebalus in the Second Battle of Tapae in 101 AD. With Trajan's troops pressing towards the Dacian capital Sarmizegethusa, Decebalus once more sought terms. Decebalus rebuilt his power over the following years and attacked Roman garrisons again in 105 AD. In response Trajan again marched into Dacia, besieging the Dacian capital in the Siege of Sarmizegethusa, and razing it to the ground. With Dacia quelled, Trajan subsequently invaded the Parthian empire to the east, his conquests taking the Roman Empire to its greatest extent. Rome's borders in the east were indirectly governed through a system of client states for some time, leading to less direct campaigning than in the west in this period.
To expand the glory of his reign, restore the finances of Rome, and end a treaty perceived as humiliating, Trajan resolved on the conquest of Dacia and with it the capture of the famous Treasure of Decebalus and control over the Dacian gold mines of Transylvania. The result of his first campaign (101–102) was the siege of the Dacian capital Sarmizegethusa and the occupation of a part of the country. The second campaign (105–106) ended with the suicide of Decebalus, and the conquest of the territory that was to form the Roman province Dacia Traiana. The history of the war is given by Cassius Dio, but the best commentary upon it is the famous Column of Trajan in Rome.
Although the Romans conquered and destroyed the ancient Kingdom of Dacia, a large remainder of the land remained outside of Roman Imperial authority. Additionally, the conquest changed the balance of power in the region and was the catalyst for a renewed alliance of Germanic and Celtic tribes and kingdoms against the Roman Empire. However, the material advantages of the Roman Imperial system wasn't lost on much of the surviving aristocracy. Thus, most of the Romanian historians and linguists believe that many of the Dacians became Romanised (see also Origin of Romanians).
Nonetheless, Germanic and Celtic kingdoms, particularly the Gothic tribes made a slow progression toward the Dacian borders and soon within a generation were making assaults on the province. Ultimately, the Goths succeeded in dislodging the Romans and restoring the independence of Dacia following Aurelian's withdrawal, in 275. The province was abandoned by Roman troops, and, according to the Breviarium historiae Romanae by Eutropius, Roman citizens "from the town and lands of Dacia" were resettled to the interior of Moesia. However, Romanian historians maintain that the bulk of the civilian population remained and a surviving aristocratic Dacian line revived the kingdom under Regalianus. About his origin, the Tyranni Triginta says he was a Dacian, a kinsman of Decebalus. Nonetheless, the Gothic aristocracy remained ascendant and through intermarriage soon dominated the kingdom which was absorbed into their larger empire.
During Diocletian, circa AD296, in order to defend the Roman border, fortifications are erected by the Romans, on both banks of the Danube.By AD336 Constantine the Great had reconquered the lost province, however following his death, the Romans abandoned Dacia for good.