Reference to a map will show a rhomboidal space of country with natural boundaries upon all sides, of which the Tigris forms the western. From it spring the others, the two Zab rivers, Lesser and Greater, running up at an angle to meet the Zagros range, which, parallel to the Tigris, makes a fourth boundary. Within these limits lies a land, part plain, part hill, well watered, and of a pleasant climate and extreme fertility, and this was Assyria proper, and the later kingdom and province of Adiabene, whose eastern border, the Zagros Mountains, harboured then, as now, hordes of savage hill people, and formed at once a barrier and a menace, even to the kings of Assyria. The northern river, that upon which we were camped, is the Greater Zab, known to the Romans as the Lycus. Its proximity to the capitals of Assyria (Kalah was at its mouth) kept it in a protected region during Assyrian times, and the first great battle recorded upon its banks is in 128 B.C., when the Assyrians were but a memory. At the spot where we camped, Indates, general of an army of Fravartish, a Parthian monarch, descending from the Median hills (Zagros), met Antiochus, a Syrian king of renown. Here a fierce battle was fought, ending in the defeat of Indates, and Antiochus erected a monument upon the spot of his victory, to commemorate the defeat of a powerful Parthian. The Lesser Zab, a smaller river, a long day’s journey across the plain, has acquired more fame in battle and history. Tiglath-Pileser I. in 1100 B.C. mentions on the famous cylinder found at Asshur, “forty-two countries altogether, and their princes from beyond the Lesser Zab, the remote forest districts at the boundaries to the land Khatti,[22] beyond the Euphrates, and into the upper sea of the setting sun,[23] my hand has conquered from the beginning of my reign until the fifth year of my rule.”[24] [Sidenote: THE LESSER ZAB] In A.D. 52, during the time of dispute between Parthians and Romans, Vologases, the Parthian king, undertook an expedition against Izates, the tributary king of Adiabene, “the land between the two rivers,” but having encamped upon the Lesser Zab, was called back suddenly southwards by rebellions in the cities there. However, the battles for which the Lesser Zab must be above all events famous, are the battles between the Khurasan forces of Abu Muslim the Abbaside and those of Abdullah ibn Marwan in A.D. 749, and between the same Khurasanis and Marwan himself, in A.D. 750, five months afterwards, in both of which battles, Marwan, the last of the long line of Ummayid khalifas, was defeated. The importance of these battles ranks as high as any in modern Eastern history, for by the decisive victories gained there, an Arab khalifate of immense power was terminated, and replaced by a Persian dynasty, the House of Abbas, of Khurasan, in Eastern Persia.