But the conquest of Gaul would be another affair. It was peopled with hardy races, who cast their greedy eyes on the empire of the Romans, or on some of its provinces, and who were being pushed forward to invasion by a still braver people beyond the Rhine,--races kindred to those Teutons whom Marius had defeated. There was no immediate danger from the Germans; but there was ultimate danger, as proved by the union they made in the time of Marcus Antoninus for the invasion of the Roman provinces. It was necessary to raise a barrier against their inundations. It was also necessary to subdue the various Celtic tribes of Gaul, who were getting restless and uneasy. There was no money in a conquest over barbarians, except so far as they could be sold into slavery; but there was danger in it. The whole country was threatened with insurrections, leagues, and invasion, from the Alps to the ocean. There was a confederacy of hostile kings and chieftains; they commanded innumerable forces; they controlled important posts and passes. The Gauls had long made fixed settlements, and had built bridges and fortresses. They were not so warlike as the Germans; but they were yet formidable enemies. United, they were like "a volcano giving signs of approaching eruption; and at any moment, and hardly without warning, another lava stream might be poured down Venetia and Lombardy." To rescue the Empire from such dangers was the work of Caesar; and it was no small undertaking. The Senate had given him unlimited power, for five years, over Gaul,--then a _terra incognita_,--an indefinite country, comprising the modern States of France, Holland, Switzerland, Belgium, and a part of Germany. Afterward the Senate extended the governorship five years more; so difficult was the work of conquest, and so formidable were the enemies. But it was danger which Caesar loved. The greater the obstacles the better was he pleased, and the greater was the scope for his genius,--which at first was not appreciated, for the best part of his life had been passed in Rome as a lawyer and orator and statesman. But he had a fine constitution, robust health, temperate habits, and unbounded energies. He was free to do as he liked with several legions, and had time to perfect his operations. And his legions were trained to every kind of labor and hardship. They could build bridges, cut down forests, and drain swamps, as well as march with a weight of eighty pounds to the man. They could make their own shoes, mend their own clothes, repair their own arms, and construct their own tents. They were as familiar with the axe and spade as they were with the lance and sword. They were inured to every kind of danger and difficulty, and not one of them was personally braver than the general who led them, or more skilful in riding a horse, or fording a river, or climbing a mountain. No one of them could be more abstemious. Luxury is not one of the peculiarities of successful generals in barbaric countries.