The Latin name - and therefore the correct name when talking about the history of Chiusi is - Clusium.
Ancient Clusium was a Roman city, one of a succession found at the site. The current municipality of Chiusi (Tuscany) partly overlaps the Roman walled city. The name Chiusi is derived from Clusium as well (Latin Clu- became Italian Chiu-). The Roman city remodeled an earlier Etruscan city, Clevsin, placed in the territory of a prehistoric culture, possibly also Etruscan or proto-Etruscan. The site, located in north central Italy on the west side of the Alps, is certainly that of Clusium and Clevsin, despite some doubts by a few. No one else in the long history of the city has ever questioned its location, which has always been commonly known.
Origin in prehistory
The origin of Clusium is lost in prehistory. By the time it appears in the History of Livy, it is already a major Etruscan city being petitioned for assistance against the republican partisans of Rome. About its life prior to that time Livy only makes a brief statement (10.25) that it was once called Camars.
Etruscan cities seemed suddenly to spring into existence without prior tradition at about 600 BC, when the orientalizing period began. A rich art and architecture then manifested itself, not unlike the orientalizing period in neighboring Hellas. The orientalizing began in coastal Etruria and rapidly spread inland over the territory of the previous Iron Age Villanovan Culture. The latter had appeared before 1000 BC and spread over the entire range of the later Etruscans.
The artifacts of the Villanovan are like those of central Europe. Whether the people came from there or only the culture has not been finally determined, nor has the ethnicity of the people. The two main theories are that they were proto-Italics or proto-Etruscans.
Villanovan pottery had been found at Chiusi. One common type is an urn for the ashes resulting from cremation dating to the 8th century BC. The urns are in the shape of wattle-and-daub huts with thatched roofs, presumably the homes of the deceased. This style of architecture is so far different from classical Etruscan that many Etruscologists have denied a continuity. On the other hand it is clear that the people of the region received a strong impetus from Greek colonies such as Cumae and from Greek immigration.
The minority theory is currently the Proto-Italic. In this theory Etruscans from the coast or from the Aegean resettled and renamed an Umbrian city called Camars, which the exponents believe means “marshland” in Italic. On enclosing the city with a wall they changed the name to “enclosure”, using an Etruscanized form, Clevsin, of the perfect passive participle, clusus, of Latin cludere, “to close.”
The theory leaves a few loose ends. Chiusi is situated on a hill in the uplands, far from the marshes of Latium. Moreover, if the Etruscans were dominant enough to take a city away from the Italics, why, speaking Etruscan, would they assign it another Italic name?
The ethnic question is more properly given consideration in the main article on the Etruscans. The majority view sees the Villanovan as proto-Etruscan, altered and thrown into preeminence by a Hellenic impetus. Italics are associated with hill cultures to the south where they first appear in history. Italic Umbria is later than the Etruscan.
Clevsin and Camars are more comfortable in their Etruscan milieu as Etruscan words. The limited known Etruscan vocabulary gives us camthi, the name of a magistracy, which might be segmented cam-thi, where –thi is a known locative ending. Ar, -arasi, -aras are plural endings of different cases. A cleva is an offering. S and -isi are genitive and dative endings. A place of magistracies or offerings is entirely harmonious with Etruscan culture and the uses of a regional capital city. Final resolution of the question waits for more evidence.
Chiusi is on a hill above the valley of the Clanis river near lake Clusium, both of which features had those names in antiquity. The Clanis is part of the Tiber drainage system and was navigable by boat from there. Rome was also accessed by the via Cassia, which was built over an Etruscan road.
The site of ancient Clusium was reoccupied in Roman and later times, obscuring and obliterating much of the Etruscan layers. For example, the ancient sources describe the tomb of Lars Porsena at Clusium as well as the sacking and levelling of the city by Sulla. Much of what remains are its tombs and its underground passages, some of which might have been associated with the monument to Porsena.
Lars Porsena, king or lucumo of Clevsin, decided not to restore the Tarquin monarchy, but fostered a republic instead. Even then Clevsin was a major city of the Etruscan League.
The Etruscan League was a legendary confederacy between 12 cities of Etruria. They met at the fanum Voltumnae (“temple of Voltumna”) at Velzna (Volsinii) once a year to choose a leader. The league usually achieves a place in the history of ancient Italy, but the sources (mainly Livy) mention two other leagues of 12 cities each that do not: one in Campania and one in the Po Valley. The total number of major Etruscan cities in Italy according to the sources is thus 36.
The Italic theory of the Villanovan Culture asks us to believe a socio-political impossibility: that around 600 BC a massive migration of Etruscans from the Aegean landed on the coast of Etruria and took the west half of Italy down to Campania as well as the Po Valley from the Italics, building 36 cities and innumerable smaller settlements, forming into three confederacies and taking over Rome as well. And yet, if that is not what happened, then the Villanovan is clearly proto-Etruscan.
Even legend accords all the time from the Trojan War to the founding of Rome for the rise of the Etruscans. The league was founded by Tyrrhenus, a character from the time of Aeneas, who fought in the Trojan War. Clusium was one of the Etruscan cities said by Virgil to have assisted Aeneas in his efforts. This Clusium can only have been Villanovan.
Questions of classical dating usually arrive at pottery as a bottom line and that is true of Clusium as well. A characteristic pottery of the 7th century, about 650-600, Bucchero ware, was manufactured there. Imported and imitated Corinthian pottery of all phases are represented at Clusium. The earliest is the Geometric style, 1000-700 BC at Corinth.
Apparently, the Etruscans were an indigenous people who became influenced by Greek culture after Mycenaean times, reaching a crescendo by 600 BC, after which Rome came to prevail. Very likely, the Camars phase and the wattle-and-daub houses were before 1000 BC.
Clusium only appears in Roman history in episodes. Centuries after Tyrrhenus, Etruscan families are ruling Rome. Lars Porsena is lucumo, or king, at Clevsin. He is dragged into the struggle between the ruling Tarquin family of Rome and the politically unhappy gentes, who want to replace monarchy with a republic.
The sources are elusive. Apparently Clusium, Arretium, Volaterrae, Rusellae and Vetulonia, all Etruscan cities, were conspiring to support the republicans. And yet, when the Tarquins were driven from Rome they demanded and received refuge at Clevsin.
Lars Porsena marched on Rome with an army and a divided mind. Lack of resolve perhaps contributed to his not taking the Pons Sublicius defended by Horatius Cocles. In legend he either took the city but turned it over to the republicans, or declined to prosecute the war further (being so impressed with Horatius’ bravery). Porsena is said to have sent his son, Aruns, to take Aricia, but the expedition failed and Aruns was killed. Clusium then vanishes from history for a few hundred years.
Pliny the Elder wrote that a magnificent tomb was built for Porsena: a large mausoleum surrounded by cascades of pyramids over a labyrinth of underground chambers in which an intruder could get lost. Pliny never saw this tomb, so his description is based on a report from Varro and perhaps a conflated comparison to the Minoan labyrinths he describes before this tomb. Large-size tumuli of the late archaic period were built at Chiusi, and modern scholars have tried to associate these (especially Poggio Gaiella), with the legendary tomb of Porsena.
Recently there was an attempt to relocate ancient Clusium to an unexplored site closer to Florence . The site (Gonfienti) has the virtue of being possible in size and structure and of being unexplored. Perhaps some evidence more definitive than what currently exists will come to light.
A Roman ally
In the early 4th century BC (391 BC according to Varronian chronology) it was besieged by Gauls, and the Clusines called upon Rome to intermediate. However, in the following negotiations one of the Roman delegates, of the gens Fabia, killed a Gallic leader. When the Romans refused to hand over the Fabii and in fact appointed two members of the family as consuls for the next year, the enraged Gauls broke up their siege and under the leadership of Brennus they marched onto and subsequently sacked Rome.