Besides forming his general plan of campaign at his leisure, and collecting, arming, and exercising his native forces, he was enabled to gain over certain chiefs upon his borders, who had hitherto held a semi-dependent position, and might have been expected to welcome the Romans.

One of these, Abgarus, prince of Osrhoene, or the tract east of the Euphrates about the city of Edessa, had been received into the Roman alliance by Pompey, but, with the fickleness common among Orientals, he now readily changed sides, and undertook to play a double part for the advantage of the Parthians.

Another, Alchaudonius, an Arab sheikh of these parts, had made his submission to Rome even earlier; but having become convinced that Parthia was the stronger power of the two, he also went over to Orodes.

The importance of these adhesions would depend greatly on the line of march which Crassus might determine to follow in making his attack.

Three plans were open to him.