Gaius Julius Caesar remains the first known governor of the Roman province of Illyricum. His proconsulship had begun in 58 BC lasting up until 50 BC. Opinion that the province of Illyricum had been established by the Lex Vatinia in 59 BC remains widespread in historiography, but theories placing its foundation in 168 BC, 118 BC and 78 BC are also existent. A hypothesis that claimed that the province was a part of the Cisalpine Gaul during Caesar's proconsulship also existed, which, however, is not supported by historical sources. Period of Caesar's proconsulship is scarcely documented in historical sources. It is known that he planned on visiting the province in 57 BC, but his plans most assuredly amounted to nothing. The following year, in Aquileia, he recieved a delegation from Illyricum, more precisely, from Salona, that asked him to arbitrate in some dispute. Said dispute was probably related to Issaeans' right to sail the Manian Bay. To ensure the implementation of his decision regarding the dispute, Caesar deployed legate Quintus Numerius Rufus to Illyricum. Caesar had first visited Illyricum in 54 BC when he ended attacks of the Pirustae on the province. During that visit he also presided a juridical convent. Before the outbreak of the civil war between Caesar and Pompey, the Delmatae conquered the town of Promona, and Caesar, at the request of the Liburni, sent an army to fight against the Delmatae. Both Caesar's army and the Liburni were defeated by the Delmatae. Battles that took place in the area of Illyricum during the civil war between Caesar and Pompey are the battle off the Island of Krk, the siege of Salona, the operation of Quintus Cornificius, the campaign of Aulus Gabinius and the battle at Tauris. The population of Illyricum choose to support either Caesar or Pompey. By the end of the first century BC, the colonies of Parentium, Iader, Salona, Narona and Epidaurum had been founded in Illyricum. There are different oppinions on whether the colonies had been founded by Caesar or Octavian (Augustus). The data provided by the historical sources can lead only to a conclusion that the colony of Iader was most probably founded by Augustus, while the question of the founder of the remaining colonies remains yet to be answered. Some historians also attribute to Caesar grants of immunity and ius Italicum to certain Liburnian communities. Up until today historiography has still not offered a satisfactory explanation as to why and when were the Liburnian communities granted these privileges.