The Cimmerians, hard pressed by the Scythians, crossed from Europe into Asia and conquered the land of the Hittites. Then they left the mountains of Asia Minor and descended into the valley of Mesopotamia, where they wrought terrible havoc among the impoverished people of the Assyrian Empire. Nineveh called for volunteers to stop this invasion. Her worn-out regiments marched northward when news came of a more immediate and formidable danger. For many years a small tribe of Semitic nomads, called the Chaldeans, had been living peacefully in the south-eastern part of the fertile valley, in the country called Ur. Suddenly these Chaldeans had gone upon the war-path and had begun a regular campaign against the Assyrians. Attacked from all sides, the Assyrian State, which had never gained the good-will of a single neighbor, was doomed to perish. When Nineveh fell and this forbidding treasure house, filled with the plunder of centuries, was at last destroyed, there was joy in every hut and hamlet from the Persian Gulf to the Nile. And when the Greeks visited the Euphrates a few generations later and asked what these vast ruins, covered with shrubs and trees might be, there was no one to tell them. The people had hastened to forget the very name of the city that had been such a cruel master and had so miserably oppressed them. Babylon, on the other hand, which had ruled its subjects in a very different way, came back to life. During the long reign of the wise King Nebuchadnezzar the ancient temples were rebuilt. Vast palaces were erected within a short space of time. New canals were dug all over the valley to help irrigate the fields. Quarrelsome neighbors were severely punished. Egypt was reduced to a mere frontier-province and Jerusalem, the capital of the Jews, was destroyed. The Holy Books of Moses were taken to Babylon and several thousand Jews were forced to follow the Babylonian King to his capital as hostages for the good behavior of those who remained behind in Palestine. But Babylon was made into one of the seven wonders of the ancient world. Trees were planted along the banks of the Euphrates. Flowers were made to grow upon the many walls of the city and after a few years it seemed that a thousand gardens were hanging from the roofs of the ancient town. As soon as the Chaldeans had made their capital the show-place of the world they devoted their attention to matters of the mind and of the spirit. Like all desert folk they were deeply interested in the stars which at night had guided them safely through the trackless desert. They studied the heavens and named the twelve signs of the Zodiak. They made maps of the sky and they discovered the first five planets. To these they gave the names of their Gods. When the Romans conquered Mesopotamia they translated the Chaldean names into Latin and that explains why today we talk of Jupiter and Venus and Mars and Mercury and Saturn.