When Rome was just a rustic settlement a trouble only to, and only troubled by, its nearest neighbours in the centre of Italy, far away to the east the Persians ruled a great empire. This empire had possessions on three continents and controlled a huge territory right up to the borders of India and including Asia Minor, Egypt and the area to the north of Greece called Thrace. Had this entity survived it would have put a considerable obstacle in the way of Roman expansion into the East.
But in one of the great upsets in history, this huge state was destroyed and destroyed utterly by one man leading a modest force of troops from an obscure kingdom. That man was Alexander the Great. On his death the Persian empire was divided between his generals. Persia itself was overrun by a tribe from the steppes called the Parthians.
The Parthians were formidable enemies and presented a barrier to any further advance eastwards, but never seriously threatened to make inroads into the empire itself. But in 226 (or 224 according to modern scholars) the situation changed. The Persians emerged from their five centuries of domination by the Greeks and the Parthians, and under a new dynasty the old Persian empire was refounded.
Ataxerxes was the name of the man that brought about this change. He had served the last king of Parthia with distinction. In fact too much distinction. He ended up becoming a threat to the monarch and was forced to rebel. His rebellion was successful, beating the Parthians in three battles in the last of which the Parthian king himself was killed. He then founded his dynasty, the Sassanids, and styled himself King of Kings, the title of the ancient kings of Persia of 500 years before.
His origins were obscure, but this enabled him to claim descent from the line of Darius, the last Persian emperor. This probably seems more reasonable to us looking back down the wrong end of the telescope from many years in the future than it did at the time. Imagine our reaction if someone turned up in Mexico claiming to be descended from Montezuma and proposing to re-establish the Aztec empire.
The Persians under Artaxerxes became once again a force to be reckoned with, and one with which Rome was obliged to reckon. They had aggressive intentions towards their long lost possessions in the middle East and Egypt. Rome now had a rival that was intent on invading and wresting away the most lucrative parts of the empire.
Where did this new found strength come from? Artaxerxes was creating a state to last. But he probably did have some anxiety about establishing his new position. He turned to one of the perennial props of governments, religion. As Jane Austen memorably put it, "It is a truth universally acknowledged, that a new monarch who needs to establish his legitimacy, must be in want of endorsement by the religious authorities."
The religion of the Persians was radically different from the polytheism of the Romans. They followed the teachings of Zoroaster. This ancient religion, which strongly influenced Judaism and Christianity, had just one God and saw the world as a battleground between good and evil. Good was represented by Ormusd, a spirit who evolved from the immeasurable time of chaos and evil that preceded the creation. He was opposed by Ahraman who emerged later to fight against all that was good. Ormusd was the creator of mankind and it ia by his power that "the motion of the planets, the order of the seasons, and the temperate mixture of the elements, are preserved."
He was a being of light and was often represented in the figure of the Sun or Mithras. In the later empire a variation of Zoroasterism that placed particular emphasis on Mithras would gain considerable support amongst the military and to be for a time a serious rival to Christianity.
Zoroaster himself was a conveniently ancient and revered figure whose writings were congenial enough as they stood and which had been added to over the years. They included the usual moral teachings that most religions had along with some local colour. The prophet was not impressed by fasting and celibacy. On the contrary enjoying life and having lots of children were encouraged. There was a lot of emphasis on carrying out useful agricultural activities. Irrigation schemes and pest control were praiseworthy. Planting trees was a saintly act - and in the parched and often hot land of Persia this probably made perfect sense.
Most importantly for an ambitious head of state, there was a large network of priests, known as magi throughout the country. Ideal for spreading propaganda and instilling a sense of national unity. The magi had considerable wealth in their own right and also received taxes from the lay population. Gibbon's notorious dislike of superstition comes to the fore as he sarcastically points out that the magi were in charge of education and no doubt made sure that the impressionable youth were brought up to appreciate the benefits of giving to the church.
One of Artaxerses earliest acts was to call a conference of the magi. This sorted out the organisation, with an arch magi to keep things under control. Some heresies were identified to justify giving the magi coercive powers. And right on cue there was a divine revelation endorsing the proceedings and getting the national religion off to a flying start. Neat.
So the new self-styled king of kings was able to create a state based on an ancient ideology and appeal to tradition. He was able to unite the Persians behind him by this combination of religion and nationalism. His problem was that he was relatively short of resources compared to the Romans. Persia was effectively a feudal economy based on agriculture, and the bulk of his troops were simply the retainers of his nobles and their farm workers pressed into service for a particular campaign. He might be able to match or exceed the Romans in raw numbers for a time, but the Roman's professional soldiers would have the upper hand in any prolonged conflict. The empire, especially in the East, was a sophisticated money based economy that could deploy its resources more efficiently. And the resources at its disposal were far more extensive. Basically Rome could only be beaten by surprise or the incompetence of its top leadership.
But it is characteristic of successful self made men that they have confidence in their own abilities, and Artaxerxes was ambitious if he was anything. He sent an message to the court of Alexander Severus delivered by 300 of his tallest and most able nobles. He demanded that the Empire withdraw from the provinces of Asia that rightly belonged to him as the descendent of Darius. War had been declared. Just like modern day Iran, Persia was thumbing its nose at a larger and more advanced western power.
The Romans gave the new king the compliment of taking him seriously and Alexander travelled to the East to take up the command of the campaign personally. For all his bravado, the ruler of Persia would have been hard put to fight off an invasion by one full scale Roman Army. The Romans attack comprised three. The plan was simple, but one that was nonetheless impossible to resist. Mesopotamia was to be invaded from the north and south simultaneously, dividing and spreading the Persian forces. Then a large thrust from the centre led by Alexander would attack now the enemy was weakened and disorganised. Artaxerxes defended with great energy and personal courage. But odds were overwhelming and unlike the Romans, losses could not be replenished. The only thing that saved the new Sassanid dynasty was weakness and indecision at the very top of the empire's command. The implementation of the plan was botched leading to much higher than necessary Roman losses, and the knock out blow was never delivered.
Artaxerxes was never to risk open war again, but he never relinquished his claims or his ambitions either. His successors were to be a constant threat to the eastern provinces. The Sassanid empire was able to treat with the Roman Empire on equal terms. This was as much a measure of the weakness of the Romans as the strength of the Persians. The relative backwardness and size of the Persian economy meant that it could never really hope to destroy Rome. The Persians could show great strength and courage individually, but they never assembled an aggressive military machine to match the legions. While a serious thorn in their side, the Persians would not threaten the very existence of the empire in the way that the German tribes would. And it is the Germans that Gibbon gives his attention to next.