The Sassanids were the last native dynasty to rule in Persia after the Parthians were overthrown, and before the Arab conquest of later centuries. Sitting astride the trade routes to the east, the Sassanid court was fabulously opulent, and the empire was dynamic and efficiently run. The military was equally efficient and dangerous, and they were a constant challenge to the Eastern Roman Empire. What caused much of the tension with the Romans was the establishment of Zoroastrianism as the state religion in Sassanid lands and the subsequent persecution of Christians. This gave the Romans a pretext for war whenever it was needed.
The Sassanids were certainly organized enough to expand their control of Armenia and to hold off the various steppe peoples. Rather than move southwards into Sassanid lands, most of these chose to head west towards the richer and far easier pickings of Rome. A strong Sassanid leader has the chance to expand westwards, while both halves of the Roman Empire are distracted by their own squabbles and barbarian hordes. Historically, the Sassanids lasted over 400 years from the fall of the Parthians until the coming of Islam and the Arabs. Islam replaced Zoroastrianism, and the Caliphate made Persia a part of a new society.
Units
Peasants
Peasants are reluctant warriors at best, but a life of endless toil and drudgery does at least produce strong backs and the ability to follow orders from your betters, even on the battlefield. Men, no matter how untrained or unready for war, are always useful in battle, and driving peasants off their lands is the quickest and cheapest way of raising a large army. Although peasants are strong, they may also be stubborn and not that keen to fight, something that a wise general bears in mind. While a warrior is trained to battle, these men are trained to the plough, and they will run if given a chance. That said, they can fight after a fashion and may do enough damage to make it worthwhile to drag them from the fields and put spears in their hands.
Kurdish Javelinmen
Kurdish Javelinmen are fleet-footed, tough skirmishers recruited from the harsh hill regions of the Sassanid Empire. They are recruited from among the independent Kurds, a people who have a long tradition of irregular warfare, as they do not accept foreign overlords easily. They are best employed to harass enemies and thin their ranks with missile volleys before the main battle is joined. They are capable of fighting hand-to-hand, but this is not their strength, and against anyone other than other skirmishers they will suffer disproportionate casualties. They carry little war gear other than their weapons, giving them their speed over rough terrain.
Levy Spearmen
Levy Spearmen are raised from the poorest in society; at best, they are men taken into the army in lieu of paying their taxes. They are given a spear, some rudimentary training, and told to obey. They are reasonably capable enough on defense but shouldn't be relied upon to fight for long against professional heavy infantry. Levies are useful for keeping cavalrymen in check -- indeed, this is their main use. Being low-status individuals -- almost with the status of state slaves -- and relatively expendable, levy spearmen are the last to receive equipment. Other than a spear, most are lucky to be given a cloth-covered wicker shield. This is good enough to make a man feel safe but rarely enough to stop a good sword swing.
Sughdian Warriors
Sughdian Warriors are the finest infantry available to the Sassanid Empire. Tough, well disciplined, heavily armed and armored, they are a match for most other civilized soldiers. Traditionally, eastern armies have always produced weak infantry types, men who are often little better -- and no more willing -- than military slaves. Sughdians, on the other hand, are a professional corps of fighters who can be expected to stand in a battle line and behave with great courage. Their equipment is lavish by the standards of previous times, and their armor is cleverly padded to give some relief under the hot sun. Sughdians should be seen as being the equals in many ways of the best of the Roman legions, and their superiors in some respects, too.
Mountain Slingers
Slingers are highly skilled troops who can bombard enemies with a hail of cruel and effective missiles. They are at risk facing light cavalry units who can ride them down. A sling is one of the simplest and oldest weapons in the world but one of the hardest to use well. Any small object can become a deadly missile for a slinger, but most are given a bag of cast lead bullets (around 25 grams in weight or so) which fly more reliably than stones picked up on the battlefield. Sling bullets might seem harmless, but when hurled at speed and with accuracy, they can bring down the strongest man, or even a horse; a skull will crack when a slinger hits home. These tough mountain men have usually relied on their skills to put meat on the table all their lives. They are also capable of defending themselves, when they must, in hand-to-hand combat.
Desert Archers
These hardy desert folk make excellent bowmen, as they cannot afford to waste a single shot when hunting. They are tough men, as a result of their harsh lives in the unforgiving sands and rocks of the desert. A punishing march across a trackless waste is the story of their everyday existence, so much so that going to war can seem like a pleasant diversion by comparison. At least when at war, they have the chance to taste the good life, enjoy some of the comforts of civilization, and grow wealthy on plunder
Camel Riders
Camel Raiders are hard-faced warriors intended to replace cavalry in desert conditions. Like cavalry, they are best used to ride down scattered enemies or to screen the main force in battle. They are especially effective against cavalry thanks to the smell of their camels -- horses cannot stand the strange smell of camels urine. Camels need careful handling -- they are bad tempered beasts -- and this is best left to the desert-born. Once recruited as "light cavalry," however, they can be a very effective force, if not quite as disciplined as other cavalry. They make up for any lack of cohesion by being individually skilled and savage.
Armored Camel RidersArmored Camel Riders are tough warriors who can replace cavalry in desert conditions. They are effective thanks to the fear caused in horses by camels. They are not the most powerful cavalry in the world, but as horses usually cannot stand the smell of camels, this rarely matters in cavalry fights. Equipped with spears and large shields, they are not at their best in a protracted melee but can be surprisingly effective when breaking up enemy formations -- especially light cavalry. Recruited from among the desert tribesmen, these men are a specific answer to the problem of fielding cavalry along wild and waterless frontiers.
Cataphracts and ClibinarriCataphracts and Clibinarri are super-heavy cavalry, with both man and horse armored from head to toe. Few can withstand their ponderous lance charge. Eastern peoples have long used heavily armored -- in this case completely armored -- horsemen in battle. Before the Sassanid dynasty took control, the Parthians had perfected these "iron warriors" as their supreme battle-winning force. Cataphracts are not the answer to every tactical problem. They are superb for breaking enemy formations, but they cannot be used for more "traditional" cavalry duties such as pursuit and screening. They are an iron fist inside a spiked iron glove, ready to deliver their commander's punch to the enemies' collective throat.
Clibinarii ImmortalsA Sassanid general has a personal guard of able and fierce Clibinarii Immortals. These "iron horsemen" are an elite to be used at the moment of crisis. These "immortals" are well trained, better armored than almost every other soldier in the world, and brutally effective. Few other men can hope to stand against an attack by these super-heavy cavalry. The only thing that they have to fear -- and this is true of all cavalrymen -- is a unit of stalwart spearmen. Even a fully armored horse will hesitate when faced with gleaming spear points. These men are best used as a mobile "hammer" to smash slow or static enemy units. They are not suited to pursuing fleeing enemies or driving off skirmishers.
ElephantsWar elephants are a rarity in war these days, but they are still terrible opponents to face. They can trample men and horses and intimidate many just by their appearance on the battlefield. Some three meters tall at the shoulder, these animals are trained only to a limited degree. They cannot be relied upon to always do what they are told, and are known to run wild in battle, crushing friends and foe alike. For this reason each elephant driver is given a spike (to drive into the base of the elephant's skull) and mallet, so that he can kill his mount if necessary. Assuming that the elephants don't run amok, they are a valuable addition to the shock element of any army. They can also be used to batter down gates and wooden defenses too.
Nomad Archer CavalryNomad Archer Cavalry are highly skilled, lightly armored, horsemen who are both tenacious and skilled in battle. Almost as a matter of course anyone from the borderlands learns to ride as soon as they can walk and to use a bow shortly afterwards. Not to do so is to invite death or enslavement by others. Nomad equipment is similar to many other steppe horsemen, and they use composite bows cunningly laminated from wood, sinew and horn to give tremendous power without needing a large bow or long pull.
BallistaeBallistae are sinew-powered weapons that can hurl spear-like bolts with considerable accuracy. These are easily capable of passing straight through a target and skewering another man, too. Although a ballista might look like an oversized crossbow its working principles are quite different. The two arms of the ballista are threaded through two ropes made from animal sinew, a naturally elastic material. When these sinews are twisted into ropes they act as enormous springs, so pulling back the arms works against this tension. When a ballista is cocked, there is a huge amount of energy (literally) tied into the sinew ropes, and this is used to fire the bolt. Care has to be taken by the crew to make sure the two springs are equally tensioned, otherwise the ballista itself will snap, probably killing anyone standing nearby. The strength given by the sinew is also the ballista's most important weakness: the sinews do not hold their tension if they get wet, so a ballista will not work to full effect in any kind of damp or wet weather. This is rarely a problem in the dry heartlands of the Sassanid Empire.
OnagersOnagers are artillery weapons that can fling rocks and incendiary pots at enemy formations and defenses. They are, however, rather slow moving and difficult to target accurately. They are named after the wild ass of the same name, a beast reputed to be stubborn, dangerous and with a tremendous kick. All three qualities can be true of the weapon, as well. Each onager is powered by a thick, twisted rope of animal sinew, the strongest and most elastic substance available to military engineers. A single throwing arm is pushed vertically through the sinew and then pulled back and held. Once loaded, the catch is released and the arm flies forwards flinging the rock payload at the enemy as it slaps into a crossbar. The tremendous energy of the release, however, makes the whole machine judder and kick, hence the name. They can be used to target slow-moving units, but they are particularly effective when suppressing enemy artillery or when used against fortifications and buildings.
Heavy OnagersHeavy Onagers are huge artillery weapons that fling devastating boulders and incendiary pots at enemy formations and defenses. They need a large crew and are vulnerable to swift-moving enemies. These weapons are best used in siege warfare, where their battering power can bring down the strongest walls over time. They can also be used to batter holes in enemy formations. Against close-packed ranks of troops, their fire is particularly deadly. These artillery pieces are named after the wild ass or onager, a beast reputed to have a tremendous kick and a bad temperament. These qualities can be true of the weapon, as well. Each onager is powered by a thick, twisted rope of animal sinew, the strongest and most elastic substance available to military engineers. A single throwing arm is pushed vertically through the sinew and then pulled back and held. Once loaded with either a mighty rock or a firepot, the catch is released and the arm flies forwards flinging the payload enormous distances. The power of the release makes the whole machine judder and kick, hence the name. They do, however, need a relatively large crew to operate at full effectiveness, as there is much physical labor involved in just cocking the mechanism before a shot.