But there still remained beyond the Alps the task of at once rounding off the Roman territory towards the north and west, and of gaining a fresh virgin soil there for Hellenic civilization and for the yet unbroken vigour of the Italic race.
Historical Significance of the Conquests of Caesar This task Gaius Caesar undertook.

It is more than an error, it is an outrage upon the sacred spirit dominant in history, to regard Gaul solely as the parade ground on which Caesar exercised himself and his legions for the impending civil war.
Though the subjugation of the west was for Caesar so far a means to an end that he laid the foundations of his later height of power in the Transalpine wars, it is the especial privilege of a statesman of genius that his means themselves are ends in their turn.

Caesar needed no doubt for his party aims a military power, but he did not conquer Gaul as a partisan.

There was a direct political necessity for Rome to meet the perpetually threatened invasion of the Germans thus early beyond the Alps, and to construct a rampart there which should secure the peace of the Roman world.

But even this important object was not the highest and ultimate reason for which Gaul was conquered by Caesar.