This part is much more interesting than the two precedents. Already it gives us an estimate of the forces allied and auxiliaries of Caesar. He sends all its cavalry ahead four thousands men. Out we let us know that the Gallic cavalry is consisted of the Gallic "nobility" we can then estimate it (a large estimate quite higher I think of reality as by using this estimate Helvetii should have 2 250 riders and not 500) to 5 % of the troops. Four thousand riders thus represent 80 000 allied on the whole, numbers that we can add with the 24 000 légionaries. The total of the forces of Caesar was to thus approach the 104 000 fighters (to be brought closer the 45 000 Helvetii who according to Caesar would have been cut down at this time by the quarter). In spite of this crushing ratio Caesar force step and after a escarmouche between the 4 000 "Roman" riders and 500 riders Helvetii (that is to say a ratio of force of 1 against 8) and the defeat of the Romans we can understand why. Caesar is thus folowed Helvetii which continued their migration while destroying the reserves of food to weaken Helvetii. One can notice here Caesar practised the same tactics as Vercingétorix a few years later and will reproach him!