And I [Shapur I] possess the lands: Persis, Parthia, Khuzistan, Maishan, Mesene, Mesopotamia, Adiabene, Arabia, Atropatene, Armenia ... Balasgan up to the Caucasus and to the 'gate of the Alans' and ... Media, Hyrcania, Margiana, Aria, and all of the eastern Parthian provinces, Kirman, Sakastan, Turgistan, Makuran, Paradene, Sind and to the borders of ... Sogdia and Tashkent and of that sea-coast Oman.
Shapur ruled an empire that stretched over the vast lands between the Euphrates and Indus Rivers. I do not know if anyone has ever measured the extent of Sassanian territories -- not that that remained constant, of course, from the time Ardashir overthrew the Parthians in 226 AD to 651, when their empire fell to the armies of Islam. But I'd be curious to know how it compared at any given time, mile for mile, with that of Rome:, the one essentially built around the Mediterranean and growing out from that (with Britain, as expected, odd man out) and the other, in a sense, following the logic of the routes of the Silk Road.
The vast extent of the Sassanian Empire was both its strength and its weakness.
When a Sassanian king took the field at the head of his army, he had, contrary to Roman reports, a standing army (Mid. Pers. spāh) under his personal command and its officers were separate from his satraps and local princes and nobility. The backbone of the spāh was its heavy-armoured cavalry "in which all the nobles and men of rank" underwent "hard service" and became professional soldiers "through military training and discipline, through constant exercise in warfare and military manoeuvres". Another elite cavalry group was the Armenian one, whom the Persians accorded particular honour. In due course the importance of the heavy cavalry increased and the distinguished horseman assumed the meaning of "knight" as in European chivalry; if not of royal blood, he ranked next to the members of the ruling families and was among the king's boon companions .
The Sassanians did not form light-armed cavalry but extensively employed, as allies or mercenaries, troops from warlike tribes who fought under their own chiefs. "The Sagestani were the bravest of all; the Gelani, Albani, and the Hephthalites, the Kushans and the Khazars were the main suppliers of light-armed cavalry. The skill of the Dailamites in the use of sword and dagger made them valuable troopers in close combat , while Arabs were efficient in desert warfare."
Battles were usually decided by the shock elite cavalry of the front line charging the opposite ranks with heavy lances while archers gave support by discharging storms of arrows. The centre, where the commander-in-chief took his position on a throne, was defended by the strongest units. The chief weakness of the Sassanian army was said to be its lack of endurance in close combat (but that could be the toll taken by repeated charges wearing heavy armour). Another reputed fault was their too great a reliance on the presence of their leader: the moment the commander fell or fled his men gave way regardless of the course of action.
But perhaps the greatest problem was the frequent need to move such troops from one end of the empire to the other (without the benefit of sea-borne transport). If the King of Kings was campaigning in India, say, when the excellent military messenger service brought news that Alexander Severus or Gordian III or or Julian the Apostate had led a great Roman army across the Euphrates in the Far West, the Romans would be deep inside Persian territory before the king could respond.
And so the Romans would have their early victories, and ecstatic reports would be sent to Rome and triumphs declared. Persicus maximus! But then, inevitably, somewhere near the Persian capital of Cteisiphon (aka Baghdad):
...smoke or a great whirling cloud of dust was seen; so that one was led to think that it was herds of wild asses, of which there is a countless number in those regions.... But no sooner had the first light of day appeared, than the glittering coats of mail, girt with bands of steel, and the gleaming cuirasses, seen from afar, showed that the king's forces were at hand.The rest is history.
Filed in haste before flying off to New York tomorrow morning. Light posting (or none) until the end of the month.
I am indebted to the excellent The Circle of Ancient Iranian Studies website, and to its article on the Sasanian Army, by Prof. A. Sh. Shahbâzi.