Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
The Euphrates Crossed
Accordingly (701) the Euphrates was crossed (near Biradjik). To reach the Tigris from this point they had the choice of two routes; either the army might move downward along the Euphrates to the latitude of Seleucia where the Euphrates and Tigris are only a few miles distant from each other; or they might immediately after crossing take the shortest line to the Tigris right across the great Mesopotamian desert. The former route led directly to the Parthian capital Ctesiphon, which lay opposite Seleucia on the other bank of the Tigris; several weighty voices were raised in favour of this route in the Roman council of war; in particular the quaestor Gaius Cassius pointed to the difficulties of the march in the desert, and to the suspicious reports arriving from the Roman garrisons on the left bank of the Euphrates as to the Parthian warlike preparations.
But in opposition to this the Arab prince Abgarus announced that the Parthians were employed in evacuating their western provinces. They had already packed up their treasures and put themselves in motion to flee to the Hyrcanians and Scythians; only through a forced march by the shortest route was it at all possible still to reach them; but by such a march the Romans would probably succeed in overtaking and cutting up at least the rear-guard of the great army under Sillaces and the vizier, and obtaining enormous spoil. These reports of the friendly Bedouins decided the direction of the march; the Roman army, consisting of seven legions, 4000 cavalry, and 4000 slingers and archers, turned off from the Euphrates and away into the inhospitable plains of northern Mesopotamia.
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