Celtic warfare
The "Gallic Wars" were a series of military campaigns waged by the Roman proconsul Julius Caesar against Gallic tribes, lasting from 58 BC to 51 BC. The Romans would also raid Britannia and Germania, but these expeditions never developed into full-scale invasions. The Gallic Wars culminated in the decisive Battle of Alesia in 52 BC, in which a complete Roman victory resulted in the expansion of the Roman Republic over the whole of Gaul. The wars paved the way for Caesar to become the sole ruler of the Roman Republic.
Diodorus Siculus
In the next section (books VII–XVII), he recounts the history of the world from the Trojan War down to the death of Alexander the Great. The last section (books XVII to the end) concerns the historical events from the successors of Alexander down to either 60 BC or the beginning of Julius Caesar's Gallic Wars. (The end has been lost, so it is unclear whether Diodorus reached the beginning of the Gallic War as he promised at the beginning of his work or, as evidence suggests, old and tired from his labours he stopped short at 60 BC.) He selected the name "Bibliotheca" in acknowledgment that he was assembling a composite work from many sources. Identified authors on whose works he drew include Hecataeus of Abdera, Ctesias of Cnidus, Ephorus, Theopompus, Hieronymus of Cardia, Duris of Samos, Diyllus, Philistus, Timaeus, Polybius, and Posidonius.