Who is Labienus from The Conquest of Gaul and what is their importance?

Titus Atius Labienus is Caesar's most able general, and invariably given the most responsible tasks. Typically, Caesar gives him command of the wintering legions when he returns to Italy at the end of a campaign. Labienus is sufficiently confident of Caesar's trust and respect that he declines to come to Caesar's aid when he finds himself threatened by the Treveri when Caesar marched to save the besieged Cicero. In the final section, there is a reference by Caesar to attempts by his enemies to alienate Labienus from Caesar's support, but he does not give any credence to these reports. History shows, however, that Labienus did fight against Caesar in the civil war that followed and died in that conflict.