Before attempting any sort of discussion of the Sassanian military it is necessary to have some knowledge of the system adopted by the Parthians. As the predecessors of the Sassanians they exerted an important influence upon their successors' military Organisation. It was perhaps the obvious inefficiencies and decentralised nature of this system which spurred Ardashir I to initiate changes.

Military Aspects of the Parthian State

The Parthian forces led to defeat by Artabanus V, c.217, probably differed little from those at the disposal of Suren when he defeated Crassus at Carrhae in 53 BC. The two conflicts were separated by a span of approximately 175 years.The disparate Parthian state did not possess a standing army. There were, however, permanent garrisons for towns and forts in addition to those retinues at the disposal of local rulers, powerful nobles and the Great King himself. It can therefore be seen that the military resources available to the state were conditioned by the system of government that prevailed.

The only permanent forces upon which the monarch could rely were those drawn from his personal estates. These were only of limited extent, thus possessing restricted manpower resources. The King was therefore dependent upon the loyalty of his nobles and their willingness to commit their own troops on his behalf should the need to put an army in the field arise. This loyalty was conditioned by the fact that the nobles influence at court was partially dependent upon their military strength, in addition to the offices and wealth held. The inherent conflict of interests that this situation presented must often have led to an apparently half-hearted response to requests for military support from the Great King, no doubt governed by thoughts of personal safety rather than national loyalty. It is perhaps significant that after the defeat of the ruler of Ahvaz by Ardashir Sassan, Artabanus V gathered together his own forces and personally led them in his final campaign. Was he unable to enlist the support of his nobles because they preferred to await the outcome of the forthcoming campaign before reaffirming their loyalty or did they they believe that a change was necessary, desirable or inevitable?

In time of need the monarch appealed to his vassals, regional and local rulers, and garrison commanders to muster what forces they could at a given location at a given time. The nobles and state officials would bring the mustered levies (hamspah) and sometimes supplemented them with foreign mercenaries. The backbone of the army (spah) and the main martial power within the state the Parthians themselves; skilled in both horsemanship and archery.

Historical experience, the geography of the region, and the organisation of the state combined to dictate that an emphasis be placed upon the cavalry element (asbaran), which possessed the necessary mobility to react to invasions and rebellions wherever they occurred. Infantry were sometimes present but only in small numbers, usually playing no significant part in the fighting. The nobles (azats) and their accompanying dependants, not slaves, thus formed the majority of the army. Since an army would contain large numbers of azat dependants, who normally worked on the land or at trades, it would of necessity be disbanded as hastily as possible in order to minimise damage to the economy. Also, the prolonged concentration of large numbers of troops represented a continued threat to the position of the Great King, which he naturally sought to dissipate as soon as prudence permitted.

The cavalry arm was formed of two distinctive troop types - lighter armed and mounted horsemen armed with bow, and possibly sword, and the sturdily mounted, heavily protected cavalry, both horse and rider wearing protective lamellar or scale armour, and armed with lance, bow and knife. These two elements combined to form a deceptively effective fighting force. The unprotected horse archers were able to provide intimidating and highly mobile support to their heavier counterparts. The lighter cavalry would use its agility to harass the opposition using hit and run tactics, dividing its forces by feigning retreat, before the co-operating heavily armed forces moved in to defeat those enemy who had survived the constant shower of missiles falling upon them.

This army was at times supported by camel-borne troops, with the heavily protected rider possessing a mount better able to withstand the rigours of campaigning than a horse. Camels were also employed on occasion to transport supplies of arrows in order to replenish the archers during an engagement. In this highly mobile combination of troops the Parthians possessed an essentially defensive force; it proved unable on many occasions to successfully retain control of conquered lands in the west, especially if faced with a well disciplined force.

Lacking the ability to defeat opposition in the field in detail without the combination of co-operation within its own ranks and favourable circumstances, a Parthian army could be, and was, forced to retire and thus abandon territorial acquisitions in the face of a well supplied adversary.

Insufficient manpower in the field to conduct siege operations, and a lack of the necessary associated technology and expertise, rendered the Parthians impotent when faced with a fortified city. Even captured siege equipment was not utilised to any advantage by an army which greatly neglected this field of warfare.

The most numerous army which took the field of battle during the Parthian era was employed against Mark Antony, in 36 BC, consisting of 400 azats and their dependants; it totaled 50,000. Though perhaps an unusually large force, Suren was able, in 53 BC, to lead an army of 1,000 heavy and 9,000 lighter cavalry, all of whom were either his dependants or bondsmen, against Crassus at Carrhae. During the Christian era the proportion of lance armed heavy cavalry to lighter cavalry increased substantially; by the time that Ardashir defeated Artabanus V, c.224 AD, they were probably more numerous than ever before though possibly less well protected. A general lightening of this element may have occurred throughout the era of Parthian domination.

As a consequence of the paucity of information available it is not possible to provide a detailed description of the Parthian army and its organisation. Complicated command structures were not, however, necessary, as there was no permanent force of greater size than one of the garrisons or the Great King's retinue.

The smallest unit of organisation was the wast, the next being the drafs, and the largest the gund. The strength of a drafs was 1,000 men, while that of a gund was 10,000. This strongly implies a decimal organisation, with the wast possessing an establishment of 100 men. The army (spah) was commanded by the Great King, his son, or a spahpat, chosen from among the ranks of the senior nobles.

More Sassanians Part One

Introduction
Heirs of the Achaemenids or a Question of Timing?
The Foundation Upon Which the Sassanians Built