this end he stirred up popular nightmares of the first sack of Rome by the Gauls and the more recent spectre of the Cimbri and Teutones. When the Helvetii and Tigurini tribes began to migrate on a route that would take them near (not into) the Roman province of Transalpine Gaul, Caesar had the barely sufficient excuse he needed for his Gallic Wars, fought between 58 BC and 49 BC. After slaughtering the Helvetii tribe, Caesar prosecuted a "long, bitter and costly" campaign against other tribes across the breadth of Gaul, many of whom had fought alongside Rome against their common enemy the Helvetii, and annexed their territory to that of Rome. Plutarch claims that the campaign cost a million Gallic lives. Although "fierce and able" the Gauls were handicapped by internal disunity and fell in a series of battles over the course of a decade. Caesar defeated the Helvetii in 58 BC at the Battle of the Arar and Battle of Bibracte, the Belgic confederacy known as the Belgae at the Battle of the Axona, the Nervii in 57 BC at the Battle of the Sabis, the Aquitani, Treviri, Tencteri, Aedui and Eburones in unknown battles, and the Veneti in 56 BC. In 55 and 54 BC he made two expeditions to Britain. In 52 BC, following the Siege of Avaricum and a string of inconclusive battles, Caesar defeated a union of Gauls led by Vercingetorix at the Battle of Alesia, completing the Roman conquest of Transalpine Gaul. By 50 BC, the entirety of Gaul lay in Roman hands. Caesar recorded his own accounts of these campaigns in Commentarii de Bello Gallico ("Commentaries on the Gallic War"). Gaul never regained its Celtic identity, never attempted another nationalist rebellion, and remained loyal to Rome until the fall of the Western Empire in 476 AD. However, although Gaul itself was to thereafter remain loyal, cracks were appearing in the political unity of Rome's governing figures – partly over concerns over the loyalty of Caesar's Gallic troops to his person rather than the state – that were soon to drive Rome into a lengthy series of civil wars. Triumvirates, Caesarian ascension, and revolt (53–30 BC) By 59 BC an unofficial political alliance known as the First Triumvirate was formed between Gaius Julius Caesar, Marcus Licinius Crassus, and Gnaeus Pompeius Magnus to share power and influence. It was always an uncomfortable alliance given