Roman authors for unknown reasons wrote that the Belli were of mixed Illyrian and Celtic (Belgic) origin and probably related with the Bellovaci, who were said to have migrated to the Iberian Peninsula around the 4th Century BC and part of the Celtiberians. There is an overwhelming amount of evidence that the ancestors of the Celtiberian groups were installed in the Meseta area of the peninsula from at least 1000 BC and probably much earlier.
The Belli inhabited the middle Jiloca and Huerva river valleys in Zaragoza province with their territories stretching up to the Guadalope and upper Turia valleys, close to their neighbours and clients, the Titii. Their early capital was Segeda (Poyo de Maya – Zaragoza; Celtiberian mint: Sekaiza), subsequently transferred to nearby Durón de Belmonte and later offset by Bilbilis (Valdeherrera, near Calatayud – Zaragoza; Celtiberian mint: Bilbiliz). Other Belli urban centers included Nertobriga (La Almunia de Doña Godina – Zaragoza; Celtiberian mint: Nertobis), Contrebia Belaisca (Zaforas de Botorita – Zaragoza; Celtiberian mint: Contebacom Bel), Beligiom (Piquete de la Atalaya de Azuara – Zaragoza; Celtiberian mint: Belikiom), Lesera (El Forcal) and Belgeda (Belchite – Zaragoza). It is plausible that by the 2nd Century BC they exerted some form of control over the strategic frontier towns of Belia (sited somewhere between the Huerva' and Aguas Vivas' rivers; Celtiberian mint: Belaiscom), Osicerda (El Palau de Alcañiz – Teruel; Iberian designation: Usercerte), Damania (Hinojosa de Jarque – Teruel; Celtiberian mint: Tamaniu) and Orosis (La Caridad de Caminreal – Teruel; Celtiberian mint: Orosiz), facing the Iberian Lobetani and Edetani peoples of the modern Valencia coastal region.
The most culturally advanced of the peoples of southern Celtiberia, the Belli were the first Celtiberian tribe to adopt coinage in the aftermath of the 2nd Punic War and to post laws in written form on bronze tablets (Tabulae), using a modified Northeastern Iberian script (known as the Celtiberian script) for their own language. In this script and language they inscribed the characteristic Celtiberian 'hospitality tokens' which are small bronze objects, in two halves, each half being retained by people who stood in hospitality relationship to one another. These would act as a sort of identity card, and were probably used as safe-conducts or other warranties. The two halves have been found in places several hundreds of kilometres apart, which implies that the various Celtic groups maintained a system of communications throughout at least central Spain. The most complete Celtiberian text we have on the bronze 'hospitality tokens' that acted as a sort of identity card is from the Belli and reads lubos alisokum aualoske kontebias belaiskas meaning 'Lubos of the Aliso family, son of Aualos, from Contrebia Belaisca' showing the self-description of this man, by paternity, extended family and territory which is characteristically Celtic.
During the 3rd-2nd centuries BC, the Belli joined the Celtiberian confederacy alongside the Arevaci, Lusones and Titii, with whom they developed close political and military ties – in 153 BC the Numantines even elected the Belli General Caros as leader of the Celtiberian coalition army that ambushed the Consul Quintus Fulvius Nobilior at the battle of Ribarroya, at the Baldano river valley in the beginning of the first Numantine War. Prior to that, they had been forced in 181 BC to accept Roman suzerainty by Tiberius Sempronius Gracchus the Elder, but this did not prevent them from resisting further Roman encroachment of their lands as well as fighting off Turboletae raids and the Iberian Lobetani people.
Defeated in 143 BC by Proconsul Quintus Caecilius Metellus Macedonicus, and faced with the fall of Numantia in 133 BC and the subsequent collapse of the Celtiberian confederacy, the Belli territory was incorporated into Hispania Citerior province though little is known of their history afterwards. The Belli appear to have remained independent until the Sertorian Wars of the early 1st Century BC, when they were gradually pushed back from the upper Jiloca by the Edetani who seized Beligiom, Belgeda, Damania and Orosis, therefore losing all the lands east of the Huerva River. Around 72 BC they and their Titii allies merged with the pro-Roman Uraci, Cratistii and Olcades tribes to form the Late Celtiberian people (Latin: Celtiberi) of romanized southern Celtiberia.
- Cremin, Aedeen (1992). The Celts in Europe. Sydney, Australia: Sydney Series in Celtic Studies 2, Centre for Celtic Studies, University of Sydney. p. 57. ISBN 0-86758-624-9.
- Pliny the Elder, Naturalis Historia, III, 29.
- Strabo, Geographikon, III, 4, 12.
- Cremin, Aedeen (1992). The Celts in Europe. Sydney, Australia: Sydney Series in Celtic Studies 2, Centre for Celtic Studies, University of Sydney. p. 60. ISBN 0-86758-624-9.
- Cremin, Aedeen (1992). The Celts in Europe. Sydney, Australia: Sydney Series in Celtic Studies 2, Centre for Celtic Studies, University of Sydney. p. 63. ISBN 0-86758-624-9.
- Appian, Iberiké 44-45.
- Diodorus Siculus, Bibliothekes Istorikes 29, 28.
- Appian, Iberiké 42.
- Appian, Iberiké 76.
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