Explanation: Despite attempts to extend initially lenient terms of surrender in Gaul, Caesar, as the war wore on, behaved according to ancient norms of warfare - which were gruesome at the best of times. Sometimes the troops would be 'let loose' on a town, other times, the population would be enslaved; in one particular incident, a group of Gauls which betrayed him after being already forgiven once had the hands cut off of all men of military age.
By contrast, during Caesar's Civil War, he was ridiculously merciful to his enemies, often immediately pardoning them and affirming their high government positions, as though they'd never taken up arms against him at all.