The Istrians are generally considered as a tribe of Illyrian race (Appian, Illyr. 8; Strab. vii. p.314; Zeuss, Die Deutschen, p. 253), and the fact that they were immediately surrounded by other Illyrian tribes is in itself a strong argument in favour of this view. Scymnus Chius alone calls them a Thracian tribe, but on what authority we know not. (Scymn. Ch. 398.) They first appear in history as taking part with the other Illyrians in their piratical expeditions, and Livy ascribes to them this character as early as B.C. 301 (Liv. x. 2); but the first occasion on which they are distinctly mentioned as joining in these enterprises is just before the Second Punic War. They were, however, severely punished; the Roman consuls M. Minucius Rufus and P. Cornelius were sent against them, and they were reduced to complete submission. (Eutrop. iii. 7; Oros. iv. 13; Zonar. viii. 20; Appian, Illyr. 8.) The next mention of them occurs in B.C. 183, when the consul M. Claudius Marcellus, after a successful campaign against the Gauls, asked and obtained permission to lead his legions into Istria. (Liv. xxxix. 55.) It does not, however, appear that this invasion produced any considerable result; but their piratical expeditions, together with the opposition offered by them to the foundation of the Roman colony of Aquileia, soon became the pretext of a fresh attack. (Id. xl. 18, 26, xli. 1.) In B.C. 178 the consul A. Manlius invaded Istria with two legions; and though he at first sustained a disaster, and narrowly escaped the capture of his camp, he recovered his position before the arrival of his colleague, M. Junius, who had been sent to his support. The two consuls now attacked and defeated the Istrians; and their successor, C. Claudius, following up this advantage, took in succession the towns of Nesactium, Mutila, and Faveria, and reduced the whole people to submission. For this success he was rewarded with a triumph, B.C. 177. (Liv. xli. 1-5, 8-13; Flor. ii. 10.) The subjection of the Istrians on this occasion seems to have been real and complete; for, though a few years after we find them joining the Carni and Iapydes in complaining of the exactions of C. Cassius (Liv. 43.5), we hear of no subsequent revolts, and the district appears to have continued tranquil under the Roman yoke, until it was incorporated by Augustus, together with Venetia and the land of the Carni, as a portion of Italy. (Strab. v. p.215; Plin. iii. 19. s. 23.) It continued thenceforth to be always included under that name, though geographically connected much more closely with Dalmatia and Illyricum. Hence we find, in the Notitia Dignitatum, the “Consularis Venetiae et Histriae” placed under the jurisdiction of the Vicarius Italiae. (Not. Dign. ii. pp. 5, 65.)

The natural limits of Istria are clearly marked by those of the peninsula of which it consists, or by a line drawn across from the Gulf of Trieste to that of Quarnero, near Fiume; but the political boundary was fixed by Augustus, when he included Istria in Italy, at the river Arsia or Arsa, which falls into the Gulf of Quarnero about 15 miles from the southern extremity of the peninsula. This river has its sources in the group of mountains of which the Monte Maggiore forms the highest point, and which constitutes the heart or nucleus of the peninsula, from which there radiate ranges of great calcareous hills, gradually declining as they approach the western coast, so that the shore of Istria along the Adriatic, though hilly and rocky, is not of any considerable elevation, or picturesque in character. But the calcareous rocks of which it is composed are indented by deep inlets, forming excellent harbours; of these, the beautiful land-locked basin of Pola is particularly remarkable, and was noted in ancient as well as modern times. The northern point of Istria was fixed by Augustus at the river Formio, a small stream falling into the Gulf of Trieste between that city and Capo d'Istria. Pliny expressly excludes Tergeste from Istria; but Ptolemy extends the limits of that province so as to include both the river Formio and Tergeste (Ptol. 3.1 § 27); and Strabo also appears to consider the Timavus as constituting the boundary of Istria (Strab. v. p.215), though he elsewhere calls Tergeste “a village of the Carni” (vii. p. 314). Pliny, however, repeatedly alludes to the Formio as having constituted the boundary of Italy before that name was officially extended so as to include Istria also, and there can be no doubt of the correctness of his statement. Istria is not a country of any great natural fertility; but its calcareous rocky soil was well adapted for the growth of olives, and its oil was reckoned by Pliny inferior only to that of Venafrum. (Plin. xv. 2. s. 3.) In the later ages of the Roman empire, when the seat of government was fixed at Ravenna, Istria became of increased importance, from its facility of communication by sea with that capital, and furnished considerable quantities of corn, as well as wine and oil. (Cassiod. Varr. xii. 23, 24.) This was probably the most flourishing period of its history. It was subsequently ravaged in succession by the Lombards, Avars, and Sclavi (P. Diac. iv. 25, 42), but appears to have continued permanently subject to the Lombard kingdom of Italy, until its destruction in A.D. 774.

The towns in Istria mentioned by ancient writers are not numerous. Much the most important was POLA, near the extreme southern promontory of the peninsula, which became a Roman colony under Augustus. Proceeding along the coast from Tergeste [Trieste] to Pola, were AEGIDA (Capo d'Istria), subsequently called Justinopolis, and PARENTIUM (Parenzo); while on the E. coast, near the mouth of the river Arsia, was situated NESACTIUM already noticed by Livy among the towns of the independent Istrians. The two other towns, Mutila and Faveria, mentioned by him in the same passage (xli. 11), are otherwise unknown, and cannot be identified. Ptolemy [74] also mentions three towns, which he places in the interior of the country, and names Pucinum, Piquentum (Πικούεντον), and Alvum or Alvon (Ἀλοῦον). Of these, Piquentum may be probably identified with Pinguente, a considerable place in the heart of the mountain district of the interior; and Alvon with Albona (called Alvona in the Tabula), which is, however, E. of the Arsa, and therefore not strictly within the Roman province of Istria. In like manner tie Pucinum of Ptolemy is evidently the same place with the “castellum, nobile vine, Pucinum” of Pliny (7.18. s. 22), which the latter places in the territory of the Carni, between the Timavus and Tergeste, and was perhaps the same with the modern Duino. Ningum, a place mentioned in the Antonine Itinerary (p. 271) between Tergeste and Parentium, cannot be determined with any certainty. The Tabula also gives two names in the NW. part of the peninsula, Quaeri and Silvo (Silvum), both of which are wholly unknown. The same authority marks three small islands off the coast of Istria, to which it gives the names of Sepomana (?), Orsaria, and Pullaria: the last is mentioned also by Pliny (3.26. s. 30), and is probably the rocky island, or rather group of islets, off the harbour of Pola, now known as Li Brioni. The other two cannot be identified, any more than the Cissa of Pliny (l.c.): the Absyrtides of the same author are the larger islands in the Golfo di Quarnero, which belong rather to Liburnia than to Istria. [ABSYRTIDES.]

The extreme southern promontory of Istria, now called Punta di Promontore, seems to have been known in ancient times as the PROMONTORIUM POLATICUM (᾿ακρωτήριον Πολατικόν, Steph; B. s. v. Πόλα). Immediately adjoining it is a deep bay or harbour, now known as the Golfo di Medolino, which must be the Portus Planaticus (probably a corruption of Flanaticus) of the Tabula.