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
Roman and Parthian Systems of Warfare
The Romans saw too late the net into which they had allowed themselves to be ensnared. With sure glance the vizier had thoroughly seen both the danger and the means of meeting it. Nothing could be accomplished against the Roman infantry of the line with Oriental infantry; so he had rid himself of it, and by sending a mass, which was useless in the main field of battle, under the personal leadership of king Orodes to Armenia, he had prevented king Artavasdes from allowing the promised 10,000 heavy cavalry to join the army of Crassus, who now painfully felt the want of them.
On the other hand the vizier met the Roman tactics, unsurpassed of their kind, with a system entirely different. His army consisted exclusively of cavalry; the line was formed of the heavy horsemen armed with long thrusting-lances, and protected, man and horse, by a coat of mail of metallic plates or a leathern doublet and by similar greaves; the mass of the troops consisted of mounted archers. As compared with these, the Romans were thoroughly inferior in the corresponding arms both as to number and excellence. Their infantry of the line, excellent as they were in close combat, whether at a short distance with the heavy javelin or in hand-to-hand combat with the sword, could not compel an army consisting merely of cavalry to come to an engagement with them; and they found, even when they did come to a hand-to-hand conflict, an equal if not superior adversary in the iron-clad hosts of lancers.
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Reference address : https://www.ellopos.net/elpenor/rome/5-09-crassus-joint-rulers.asp?pg=7