Meanwhile the kingdom of Israel was passing into an empire. Joab and his veterans gained victory after victory, and the Hebrew army became what the Assyrian army was in later days, the most highly disciplined and irresistible force in western Asia. Moab and Ammon were subdued; the Aramaic kinglets to the north-east were made tributaries, and the kingdom of Zobah, which had risen on the ruins of the Hittite power, was overthrown. The limits of David's rule were extended to the banks of the Euphrates, and the Syrians on either side of the river were utterly crushed. Even Edom, which had successfully defied the Pharaohs in the days of Egyptian greatness, was compelled to submit to the Jewish conqueror; its male population was mercilessly massacred, and its ports on the Gulf of Suez fell into Israelitish hands. In the north Hamath made alliance with the new power that had arisen in the Oriental world, while Hiram of Tyre was glad to call himself the friend of the Israelitish king, and to furnish him with skilled workmen and articles of luxury. The latter years of David were troubled by revolts which had their origin partly in the polygamy in which he had indulged, partly in the discontent of a people still imperfectly welded together, and restless under military conscription. His son Solomon secured his throne by putting to death all possible rivals or opponents, including the grey-haired Joab. Solomon was cultured and well-educated, but his culture was selfish, and his extravagance knew no bounds. Palaces were built at Jerusalem in imitation of those of Phoenicia or Egypt, and Phoenician architects and artisans erected there a sumptuous temple in honour of the national God. Trade was encouraged and developed: the possession of the Edomite seaports gave Solomon the command of the Arabian trade, while his alliance with Hiram opened to him the harbours of the Mediterranean coast. But the wealth which David had accumulated, the tribute of the conquered provinces, and the trading monopolies of the king himself did not suffice for the extravagance of his expenditure, and heavy fiscal burdens had to be laid on the Israelitish tribes. Disaffection grew up everywhere except in Judah, where the king resided, and where the wealth raised elsewhere was spent.