Now came, however, a more serious struggle. Ararat had recovered from the blow it had received at the hands of Tiglath-pileser, and had organised a general confederacy of the northern nations against their dangerous neighbour. For six years the struggle continued. But it ended in victory for the Assyrians. Carchemish, the Hittite stronghold which commanded the road across the Euphrates, was taken in B.C. 717, and the way lay open to the west. The barrier that had existed for seven centuries between the Semites of the east and west was removed, and the last relic of the Hittite conquests in Syria passed away. In the following year Sargon overran the territories of the Minni between Ararat and Lake Urumiyeh, and two years later the northern confederacy was utterly crushed. The fortress of Muzazir, under Mount Rowandiz, was added to the Assyrian dominions, its gods were carried into captivity, and the King of Ararat committed suicide in despair. From henceforward Assyria had nothing to fear on the side of the north. The turn of the Medes came next. They were compelled to acknowledge the supremacy of Nineveh; so also was the kingdom of Ellipi, the later Ekbatana. Sargon could now turn his attention to Babylonia.

Merodach-baladan had foreseen the coming storm, and had done his best to secure allies. An alliance was made with the Elamites, who were alarmed at the conquest of Ellipi; and ambassadors were sent to Palestine (in B.C. 711), there to arrange a general rising of the population, simultaneously with the outbreak of war between Sargon and the Babylonian king. But before the confederates were ready to move, Sargon had fallen upon them separately. Ashdod, the centre of the revolt in the west, was invested and taken by the Turtannu or commander-in-chief; its ruler, a certain "Greek," who had been raised to power by the anti-Assyrian party, fled to the Arabian desert in the vain hope of saving his life, and Judah, Moab, and Edom were forced to renew their tribute. The Egyptians, who had promised to assist the rebels in Palestine, prudently retired, and the Assyrian yoke was fixed more firmly than ever upon the nations of Syria. Merodach-baladan was left to face his foe alone. In B.C. 709 he was driven out of Babylon, and forced to take refuge in his ancestral kingdom in the marshes. Sargon entered Babylon in triumph, and "took the hands of Bel." His title to rule was acknowledged by the god and the priesthood, and an Assyrian was once more the lord of western Asia.

Four years later the old warrior was murdered by a soldier, and on the 12th of Ab, or July, his son Sennacherib was proclaimed king. Sennacherib was a different man from his father. Sargon had been an able and energetic general, rough perhaps and uncultured, but vigorous and determined. His son was weak and boastful, and under him the newly-formed Assyrian empire met with its first check. It is significant that the Babylonian priests never acknowledged him as the successor of their ancient kings; he revenged himself by razing the city and sanctuary of Bel to the ground.

Merodach-baladan re-entered Babylon immediately after the death of Sargon in B.C. 705, but he was soon driven back to his retreat in the Chaldæan marshes, and an Assyrian named Bel-ibni was appointed king in his place. The next campaign of importance undertaken by Sennacherib was in B.C. 701. Palestine had revolted, under the leadership of Hezekiah of Judah. The full strength of the Assyrian army was accordingly hurled against it. The King of Sidon fled to Cyprus, and Phoenicia, Ammon, Moab, and Edom hastened to submit to their dangerous foe. Hezekiah and his Philistine vassals alone ventured to resist.

The Philistines, however, were soon subdued. A new king was appointed over Ashkelon, and Hezekiah was compelled to restore to Ekron its former prince, whom he had imprisoned in Jerusalem on account of his loyalty to Assyria. The priests and nobles of Ekron, who had given him up to Hezekiah, were ruthlessly impaled. Meanwhile Tirhakah, the Ethiopian king of Egypt, on whose help Hezekiah had relied, was marching to the assistance of his ally. Sennacherib met him at Eltekeh, and there the combined forces of the Egyptians and Arabians were defeated and compelled to retreat. Hezekiah now endeavoured to make peace by the offer of rich and numerous presents, including thirty talents of gold and 800 of silver. But nothing short of the death of the Jewish king and the transportation of his people would content the invader. Hezekiah accordingly shut himself up within the strong walls of his capital, while the Assyrians ravaged the rest of the country and prepared to besiege Jerusalem. The cities and villages were destroyed, and 200,150 persons were led away into captivity. But at this moment a catastrophe befell the Assyrians which saved Hezekiah and "the remnant" of Israel. The angel of death smote the Assyrian army, and it was decimated by a sudden pestilence. Sennacherib fled from the plague-stricken camp, carrying with him his spoil and captives, and the scanty relics of his troops. It was the last time he marched to the west, and his rebellious vassal remained unpunished.

In the following year troubles in Babylonia called him to the south. Merodach-baladan was hunted out of the marshes, and fled with his subjects across the Persian Gulf to the opposite coast of Elam, while a son of Sennacherib was made king of Babylon. But his reign did not last long. Six years later he was carried off to Elam, and a new king of native origin, Nergal-yusezib by name, was proclaimed by the Elamites. This was in return for an attack made by Sennacherib upon the Chaldæan colony in Elam, where the followers of Merodach-baladan had found a refuge. Sennacherib had caused ships to be built at Nineveh by Phoenician workmen, and had manned them with Tyrian, Sidonian, and Ionian sailors who were prisoners of war. The ships sailed down to the Tigris and across the gulf, and then fell unexpectedly upon the Chaldæans, burning their settlement, and carrying away all who had escaped massacre.

Nergal-yusezib had reigned only one year when he was defeated and captured in battle by the Assyrians; but the Elamites were still predominant in Babylonia, and another Babylonian, Musezib-Merodach, was set upon the throne of the distracted country (B.C. 693). In B.C. 691 Sennacherib once more entered it, with an overwhelming army, determined to crush all opposition. But the battle of Khalulê, fought between the Assyrians on the one side, and the combined Babylonians and Elamites on the other, led to no definite result. Sennacherib, indeed, claimed the victory, but so he had also done in the case of the campaign against Hezekiah. Two years more were needed before the Babylonians at last yielded to the superior forces of their enemy. In B.C. 689 Babylon was taken by storm, and a savage vengeance wreaked upon it. The sacred city of western Asia was levelled with the dust, the temple of Bel himself was not spared, and the Arakhtu canal which flowed past it was choked with ruins. The Babylonian chronicler tells us that for eight years there were "no kings;" the image of Bel-Merodach had been cast to the ground by the sacrilegious conqueror, and there was none who could legitimise his right to rule.

On the 20th of Tebet, or December, B.C. 681, Sennacherib was murdered by his two sons, and the Babylonians saw in the deed the punishment of his crimes. His favourite son, Esar-haddon, was at the time commanding the Assyrian army in a war against Erimenas of Ararat. As soon as the news of the murder reached him, he determined to dispute the crown with his brothers, and accordingly marched against them. They were in no position to resist him, and after holding Nineveh for forty-two days, fled to the court of the Armenian king. Esar-haddon followed, and a battle fought near Malatiyeh, on the 12th of Iyyar, or April, B.C. 680, decided the fate of the empire. The veterans of Esar-haddon utterly defeated the conspirators and their Armenian allies, and at the close of the day he was saluted as king. He then returned to Nineveh, and on the 8th of Sivan, or May, formally ascended the throne.

Esar-haddon proved himself to be not only one of the best generals Assyria ever produced, but a great administrator as well. He endeavoured to cement his empire together by a policy of reconciliation, and one of his first actions was to rebuild Babylon, to bring back to it its gods and people, and to make it one of the royal residences. Bel acknowledged him as his adopted son, and for twelve years Esar-haddon ruled over western Asia by right divine as well as by the right of conquest.

But a terrible danger menaced Assyria and the rest of the civilised Oriental world at the very beginning of his reign. Sennacherib's conquest of Ellipi, and the wars against Ararat and Minni, had weakened the barriers which protected the Assyrian empire from the incursions of the barbarians of the north. The Gimirrâ or Kimmerians, the Gomer of the Old Testament, driven by the Scyths from their seats on the Dniester and the Sea of Azof, suddenly appeared on the horizon of western Asia. Swarming through the territories of the Minni to the east of Ararat, they swooped down upon the Assyrian frontier, along with other northern nations from Media, Sepharad, and Ashchenaz. While a body of Kimmerians under Teuspa marched westward, the rest of the allies, under Kastarit or Kyaxares of Karu-Kassi, attacked the fortresses which defended Assyria on the north-east. At Nineveh all was consternation, and public prayers, accompanied by fasting, were ordered to be offered up for a hundred days and nights to the Sun-god, that he might "forgive the sin" of his people, and avert the dangers that threatened them. The prayers were heard, and the invaders were driven into Ellipi. Then Esar-haddon marched against Teuspa, and forced him to turn from Assyria. The Kimmerians made their way instead into Asia Minor, where they sacked the Greek and Phrygian cities, and overran Lydia.