Question: In pre-Roman Gaul the Belgic tribe of the Veliocasses or Velocasses controlled a large area in the lower Seine valley, which retains a trace of their name, as the Vexin, in 52 they raised 3000 men to support which son of Celtillus the Avernian, leader of the Gallic tribes?

<P0-S0> The Segni (sometimes Segui) were a tribe living in Belgic Gaul when Julius Caesar's Roman forces entered the area in 57 BCE. <P0-S1>  They are known from his account of the "Gallic War". <P0-S2>  They were one of a group of tribes listed by his local informants as the "Germani" of Belgian Gaul, along with the Eburones, Condrusi, Paemani (or Caemani), and Caeroesi (or Caeraesi). <P0-S3>  The Segni do not appear in the first listing of the Germani, which was a listing of Germani sending men to fight Caesar. <P0-S4>  But they appear in a later mention, after the defeat of the Eburones: The Segui and Condrusi, of the nation and number of the Germans ["Germani"], and who are between the Eburones and the Treviri, sent embassadors to Caesar to entreat that he would not regard them in the number of his enemies, nor consider that the cause of all the Germans on this side the Rhine was one and the same; that they had formed no plans of war, and had sent no auxiliaries to Ambiorix. <P0-S5>  Caesar, having ascertained this fact by an examination of his prisoners, commanded that if any of the Eburones in their flight had repaired to them, they should be sent back to him; he assures them that if they did that, he will not injure their territories. <SEP> <P1-S0> In pre-Roman Gaul the Belgic tribe of the Veliocasses or Velocasses controlled a large area in the lower Seine valley, which retains a trace of their name, as the Vexin. <P1-S1>  In 52 they raised 3000 men to support Vercingetorix, and fought alongside the Bellovaci in the final rebellion against Roman hegemony. <P1-S2>  According to Julius Caesar' "Commentary on the Gallic Wars" the Veliocasses participated in the tribal coalition of the Belgae that resisted the Romans in 57 BCE. <SEP> <P2-S0> Rouen, France, was founded by the Gaulish tribe of Veliocasses, who controlled a large area in the lower Seine valley, which today retains a trace of their name as the Vexin. <P2-S1>  The Gauls named the settlement "Ratumacos" and the Romans called it "Rotomagus". <P2-S2>  Roman Rotomagus was the second city of Gallia Lugdunensis, after Lugdunum (Lyon). <P2-S3>  After the reorganization of the empire by Diocletian, Rouen became the chief city of the divided province of Gallia Lugdunensis II and reached the peak of its Roman development, with an amphitheatre and "thermae", the foundations of which remain today. <P2-S4>  In the 5th century, it became the seat of a bishopric and later a capital of Merovingian Neustria. <SEP> <P3-S0>  Vercingetorix came to power after his formal designation as chieftain of the Arverni at the oppidum Gergovia in 52 BC. <P3-S1>  He immediately established an alliance with other Gallic tribes, took command and combined all forces, and led them in the Celts' most significant revolt against Roman power. <P3-S2>  He won the Battle of Gergovia against Julius Caesar in which several thousands Romans and allies died and Caesar's Roman legions withdrew. <P3-S3> Vercingetorix was the son of Celtillus the Avernian, leader of the Gallic tribes.