The author analyzes and interprets the data and evaluates historical information in the Breviarium of Festus, a fourth century Latin source. pertinent to ancient history of Croatian historical area. Although the Breviarium does not provide much data on account of its brevity. its value,in some points,must not be overiooked. Moreover,the data should be carefully examined because the explanation of certain crusial events in ancient history of the Caroatian lands depends heavily on their correct interpretation. For example, should we choose to accept, as some do, that Festus' account on expulsion of the Marcomanni and Quadi from environs of the future province of Valeria refers to Augustus' time, then this testimony might be taken as a direct proof for the assumption that the Pannonian area north of the Drava was firmly in Roman control already at that time. The most valuable piece of information for the history of Croatian lands during the Early Roman Empire provided by Festus is the mention of the Amantini as a Pannonian people after whose subjugation ended the Roman conquest of the area between the rivers of Sava and Drava. This, combined with the data from other sources, helps the historians to form a picture of Breuci and Amantini as the leaders of resistance against the Roman expansion in the Sava-Drava interamnium. The information about establishment (or restoration, to be more precise) of the Danubian limes after Marcus Aurelius' wars against the Marcomanni and Quadi is also valuable. Many inscriptions from the late second century A.D. discovered near Danube in Lower Pannonia confirm significant work on fortification of Pannonian section of the limes. As for the Later Roman Empire, the Breviarium provides excellent and often used evidence about administrative extent of Illyricum and the number of its provinces in the mid-4th century A.D. This information is of much importance because one has to be very careful in determining the exact size of Illyricum in different times during the Roman Empire. Another distinctive feature of Festus' Breviarium is the use of the form Illyricus for the usual Illyricum, and of the syntagm regio saviensis for the province of Pannonia Savia. Finally, the historical value of the Breviarium is also that it provides a testimony for the perception of a 4th century author about the main features and stages of the Roman conquest in the Croatian historical area, especially with reference to the most important peoples (Histri, Liburni, Delmatae), and personalities (Gentius, Bato), after whose vanquishment the Roman conquest was finalized and secured. With regard to this, there is much attention devoted to Pannonia, especially the region between the Sava and the Drava rivers, which might be explained by the fact that Festus' employer, Emperor Valens, was of Pannonian descent.
