His stay there was, however, abruptly cut short as, owing to the acuteness of the war with the Marcomanni and Jazyges, he had to return again to the fighting line. The Romans once more met with severe defeats. Two commanders fell; and it was not till A.D. 172 that the tide of victory turned. In that year the Marcomanni suffered an overwhelming defeat and the Emperor assumed the title _Germanicus_. But in the meantime the Quadi had rebelled and driven out their king, who was a friend of the Romans, and elected one opposed to Rome. Marcus then turned his attention to these: he set a price of 1,000 pieces of gold on the head of the rebel king; and on his being betrayed sent him to Alexandria. During one of these campaigns against the Quadi occurred the incident of the “thundering legion”--a story famous in the early Church and much controverted. It is interesting as bringing Marcus and the Christians face to face for the first time. It was during the hot summer months that a legion containing many Christians was surrounded by the Quadi in a wooded and hilly country. They were cut off from all means of getting water, and suffered terribly from the heat and thirst. In these straits, the story goes on to say, the Christians in the legion knelt and prayed for release; and lo! suddenly the whole heavens became overcast; a storm gathered and broke over the opposing forces; rain fell abundantly and the Romans gathered it in their helmets and in the hollows of their shields, and drank eagerly and gave to drink to their horses. The barbarians saw that they must now attack before the Romans recovered strength. But the rain which had refreshed the Romans turned to blinding hail against their foes; and the rain and the lightning “burnt them like oil insomuch as they wounded one another to extinguish the fire with blood.” Many, seeing such evident favour from heaven for the Roman cause, went over to their side; and Marcus Aurelius received them mercifully.