ablished Roman policy toward relationships with allies to provide justification and leverage for the expansion of Roman power across Gaul. Attacks on Roman allies were used as pretext for the subjection of those allies' neighbors. Likewise, the rise of anti-Roman factions within allied tribes was used to justify the forcible re-imposition of pro-Roman leaders, under conditions that invariably strengthened the Roman hold on these tribes. The initial cause of war was the intended mass migration of the Helvetii, a scheme which according to Caesar was originally contrived by an ambitious chieftain named Orgetorix, but which the Helvetii continued to pursue even after Orgetorix's fall and death. The intended line of march would pass through the existing Roman Province, and intervention was thus well within even a narrow interpretation of Caesar's responsibilities.
However, the intentions of the Helvetii also involved them in conflict with the Aedui, a tribe friendly to Rome. Caesar chose to expand his brief to include defense of the Aedui. This decision was reasonable enough, but in moving the zone of action outside of Roman territory it was the first step in the expansion of the war. As Caesar demanded that the Aedui follow through on their committments undertaken as an ally, that tribe fell into internal disputes, which in turn allowed Caesar to involve himself in Aedui internal affairs. Thus, in this opening phase of the war, and in the successive campaigns that followed, established Roman strategies for political expansion were put into play: first, committing Rome to the defense of an ally, then intervening in the ally's domestic politics to bind it more closely to Rome.
Caesar's strategic procedure of innovation based on precedent was mirrored on the military level. The Roman army was in modern terms an army configured for "conventional" war against centralized enemy powers fielding conventional armies of their...