The power of the Roman Empire was founded mainly on its organization. When this disintegrated, the tribes of the north could harass the empire at will. The last successful campaign against them was by Julian the Apostate, who defeated them on the Rhine in 357 A.D. He tried to restore paganism to the Roman Empire and he was tolerant toward the Jews and promised to rebuild the temple in Jerusalem. His plans for putting the old gods of the orient back on the throne did not materialize, as he was killed in his war against the Persians and all his plans for restoring the Roman Empire were buried with him. The tide of the northern tribes rose again. It culminated with the invasion by the Huns and Mongol tribes coming from the vast plains of Asia (370 A.D.). They expelled the West Goths (or Visigoths), who were permitted to cross the Danube and settle in the Roman Empire, where they joined the army and reached high posts in the Roman administration. The movement of the Germans to the south continued. They plundered Athens and Rome, and the Vandals took Spain and established themselves in northern Africa. Was the Hun invasion a function of a climatic change which forced them to look for grazing grounds outside the wide steppes of Central Asia? At this stage of the research, it is difficult to say, as we do not yet have enough paleo-climatic data from Central Asia. The data from the Fertile Crescent and Europe show that, during the fifth century, the climate was becoming generally warmer and thus also dryer. Might this have had an effect also on the steppes of Asia?