Alexander’s Impossible Conquest Explained

Ajouté : 2026-05-09

[00:00:05]The conquest of the Achaemenid Empire by the  Greek forces of Alexander III of Macedon is rightly perceived as one of the most important  events in world history. Leading a highly efficient and innovative military force, the  young Macedonian general managed to conquer the largest superpower the Earth had ever seen up  to that point. Many scholars have tried to answer the question of why Alexander achieved this feat.  Sometimes the role is attributed to Alexander’s strategic genius or to the supposed incompetence  of his rival, Darius III of Persia. The truth, as with any grand-scale military endeavour, lies  in a convergence of factors - from the legacy Alexander inherited from his father Philip, to  the structural weaknesses of the Persian Empire, to Alexander’s own remarkable capacity  for military and political improvisation.

[00:01:01]● Background Factors: The first aspect that led to the Alexandrian onslaught through Iran has very  little to do with either Alexander or his rival, Darius III. That factor is simply the background  of the states and societies in which both rulers grew up before their titanic clashes at Issus  and Gaugamela. Alexander, while undoubtedly a military mastermind, could not have achieved  his goals without the legacy of his father, Philip II of Macedon. Philip was both a seminal  military reformer and a shrewd diplomat, points which we have discussed in our previous videos and  on our members-only series on the grand statesman.

[00:02:23]When Philip came to power, Macedon was under  threat from the Illyrian kingdoms to the north and was, at best, a secondary power in Hellas.  His military reforms with innovations such as sappers and siege engines, as well as formalising  the use of the long-spear known as the Sarissa, turned the kingdom into a powerhouse in Greece.  He also managed to either annex or vassalise the whole of Greece through military campaigns  and the League of Corinth; his whole military career in the second half of the 4th century  BCE was devoted to this affair. In addition, Philip also had plans for attacking Persia, and  had already sent some preliminary contingents to Asia Minor that Alexander could use when he  began his operations. Thus, Alexander inherited a strong military from his father, one with  experience and strategic cohesion. In addition, the Greek allies of the Macedonians provided  him with both security on his southern flank in Hellas and additional military personnel  that contributed to his success in Persia.

[00:03:28]If we turn our eyes to the east, we will find that  Darius III faced a trickier situation to manage, for the Achaemenid Persian empire was less stable  than it had been under Darius I and Xerxes in the 5th Century BCE. Our sources about 4th-century  Persia are scarce, and often only Greek in character, with the usual anti-Persian biases that  imply. But some information reveals the fragmented nature of Persia at the time. Before Darius,  the previous Shahanshah was Arses, who seems to have ruled only for two years, 338-336. He was  allegedly under the control of a eunuch called Bagoas, but this might be a fanciful tale by the  Greeks who wished to denigrate the Achaemenids.

[00:04:14]Before him, Artaxerxes III ruled for about 20  years but had to deal with various revolts, including one in Egypt, which had been independent  of Persia for almost six decades. His own father, Artaxerxes II, also had to fight against his  brother Cyrus for control of the throne, where the Athenian soldier and writer Xenophon served, later  recording the experience in his Anabasis. Thus, the political environment was rather unstable  by the time Darius came to power. The young Shahanshah is often unfairly portrayed in the  sources as a coward or a weakling, but the truth is that he faced a far harder context to contend  with once he came to power. Political success is often just as much about circumstances as it  is about skills, and in the case of Darius, he inherited a far less robust empire than Alexander.  The Greek general had a strong foundation to build upon, and he used that to his utmost advantage,  whereas Darius had to contend with what he had.

[00:05:17]● Military Factors: Besides the background factors which gave Alexander an advantage,  there was also the most fundamental of aspects; that of military innovation. Here, the  importance of Alexander’s capacities as commander and tactician came to the fore on more  than one occasion. The Greek army, which marched into Asia Minor in 334 BCE, was a flexible and  well-trained military machine. Among its ranks lay Greek troops working as both hoplites and  peltasts, as well as experienced mercenaries from the Balkans. The Macedonians, especially  the Companions who served with Alexander, were also from aristocratic families that had risen  through the ranks on the basis of their talent, enabling them to devise masterful military  strategies. Other innovative specialist units, such as the hypaspists, who had light-infantry  capabilities, also provided the young king with flexibility on the battlefield. In addition,  Alexander’s pezhetairoi were defined by their use of the Sarissa, an innovation that enabled greater  control over how battles unfolded, thanks to the power of distance. This is most evident in the  battle of Gaugamela in 331 BCE, where Alexander’s ability to use all these tools came to the fore.  In this decisive third clash with Darius III, Alexander managed to turn the tables of the battle  through military improvisation. During the battle, the Persians managed to pin the Greeks' flanks  with their cavalry and chariots, partly lured by Alexander himself and his companions on the right  flank of the Hellenes. However, Alexander managed to use his rear guard to charge from the right  wing of the centre formation and break into the Persian centre at the back of the battlefield.  The chariots were unable to turn in time, too busy with the Greek flanks. Eventually, Darius had  to flee for fear of being surrounded and captured, defeated by Alexander’s military skills. Darius’s  military forces were not incapable of fighting wars; far from it, in fact. The Achaemenid  armies were always a cosmopolitan behemoth of the finest of the thousand nations  ruled by the Achaemenid empire. However, the aforementioned political turmoil within the  rather labyrinthine structures of the Achaemenid court meant that Darius was not as able to counter  Alexander’s march. For instance, Darius did indeed prepare for the Greek attack, ordering the satraps  of Asia Minor to fight off the Hellenes. However, there were military issues on multiple fronts in  the late 330s BCE, including a revolt in Egypt.

[00:07:55]Thus, Darius had to both prepare for Alexander’s  coming, but also tame the breadbasket of his empire. Unfortunately for Darius, by the time  he managed to bring some stability to Egypt, Alexander had established a foothold in Asia Minor  upon his victory in the Battle of Granicus. The Persian military was also great in numbers, but in  the two battles in which Darius fought Alexander, Issus and Gaugamela, it proved to be unable to  adapt quickly to the tides of the battle. Many explanations have been given for this weakness,  from bad leadership by Darius himself to the choice of battlefield terrain at the Battle of  Issus to inflexibility in battle tactics. Whatever the case, Alexander’s military capacities were  both more robust and more adaptable than those of Darius. Thus, when the two titans clashed, Persian  numbers could not overcome Greek phalanxes.

[00:08:48]● Logistical Factors: Alexander’s success, at least in the first decisive half of  the expedition across Persia’s realm, also highly depended on logistical masterstrokes.  In our previous video on Alexander’s logistics, we mentioned that Alexander’s troops carried  a lighter load than previous Greek forces and rarely used carts. This flexibility of movement  was important throughout Alexander’s campaigns, but in Asia Minor and the Levant, he had one  further logistical boon. Alexander’s naval support followed him throughout Asia Minor as well  as the Levant, through his important battles in Tyre and Gaza. They provided him with logistical  and provisional support as the general solidified his control over the western parts of the Persian  Empire. In addition, Asia Minor’s populations included Greeks who were friendly to Alexander  and gleefully gave him supplies for his early campaigns of the 330s. Many Levantine and Cypriot  cities also submitted and fed Alexander’s troops, despite the famous resistance of the Tyrians. And  of course, the Egyptians who controlled the great agricultural wealth of the Nile River eagerly  saw Alexander as a liberator from the Persians they so often revolted against. Alexander’s  logistics strained on occasion in Asia Minor, but only really became unsustainable when he  chased after the usurper and murderer of Darius, Bessus. In Bactria, Sogdiana, Gandhara,  and Arachosia, where the terrain was far from Persepolis and rather harsh, Alexander’s  army did indeed struggle. It was only when they found local support, like when Gandharan  kings allied with him, that Alexander was spared complete oblivion. Our sources on the  logistics of Darius III are almost non-existent, so we must speculate based on the Persian Empire’s  issues at the time. Darius does seem to have been able to sustain large armies on the march and to  have provisioned his forward operating hubs in Asia Minor that were manned by local satraps.  We must also not forget that his forces were multinational and could draw resources from across  the empire. It was thus not a question of how many provisions Darius could acquire, but of where and  how to utilise them. The main disadvantage of his logistics may have stemmed from the army's large  size; it was likely less flexible than Alexander’s forces. Whereas the Greeks could cover long  distances with some ease, the Persians still had to maintain their massive trains of supplies and  equipment, along with a larger number of servile populations to fill support roles such as cooking  and smithing. In addition, the loss of control over Asia Minor and Egypt cost the Achaemenid  forces dearly, for now their main supply lines had to come from farther in from Persia itself.  Thus, the local logistics of the Persians, who were meant to defend against Alexander  until Darius amassed his tremendous forces, had to rely on often unstable and desertion-prone  local collaborators. The major defeats that Darius faced at Issus and Gaugamela likely shattered his  logistical network, and when Alexander captured Persepolis, Darius lost most of the legitimacy  that had allowed him to muster many resources.

[00:12:06]● Propaganda Factors: Wars of conquest are often just as much won by rhetoric as by arms,  and here is where another convergence of circumstances contributed to Alexander’s victory  over Darius. The Macedonian youth who entered Asia Minor after subduing rebels in the Balkans had an  ideological mission he preached wherever he went: the liberation of the Greeks of Asia Minor  from the Persian yoke and vengeance for the Persian invasion of Hellas a century and a half  prior. Or at least, that is what he claimed to his Greek audiences. In reality, Alexander was a  masterful political propagandist, keenly adapting his message to whoever he was addressing. For the  Greeks, he focused on his anti-Persian pedigree and on the liberation of the Hellenes of Asia. But  when he went to the Levant and Egypt, he behaved as both their liberator and a man who wished to  engage with the local cultures. When he ended up taking the family of Darius hostage, he is also  said to have treated them with respect. Over time, and to the dismay of many of his Companions,  he adopted certain local elements in clothing and ruling style. For example, he tried to  incorporate the Persian customs of the Royal Tent and proskynesis, or prostrating oneself  before the King of Kings, into the way he was addressed. As we discussed in our ‘Persianisation  of Alexander’ video, the Macedonian general hoped to build an ideology of universal monarchy using  both Greek and Persian elements, a propaganda tactic which allowed him to assert his control  over most of the Persian Empire. His propaganda tactics may have alienated some of his Companions  at times, but they gained him support and rapport with local elites throughout the Persian Empire.  Alexander’s political theatre allowed him to assert control over the lands he took by the sword  and spear. In the case of Darius, we have little surviving of his propaganda efforts to rally the  empire to his side. Given that he was a distant relative of the Achaemenids, his claim to the  throne must have been weak at first. And yet he managed to survive on the throne for almost six  years and amass a large army against Alexander, only losing legitimacy when the latter defeated  him decisively in battle. Nor can we readily accept claims that Darius was weak because of  the presence of the eunuch Bagoas at court. This is because our sources discussing the matter  are Greek and thus heavily biased in favour of Alexander. What appears to have been the main  issue of Darius’s own political manoeuvring was that the Achaemenid Empire was already strained  from political turmoil. For the Levantine and Egyptian audiences that received Alexander,  the propaganda of the King of Kings seemed far less believable after decades of turmoil and  revolts. The only remaining audience that Darius could rely on, the Persian elites, probably  could not reconcile his claim to fame and kingship when Alexander achieved his victory in  Gaugamela. The recent history of the Achaemenid Empire made Darius’s political and rhetorical  manoeuvring much more difficult than Alexander’s, who was a new power whose ideology was not  yet tainted by decades of imperial overreach.

[00:15:25]● Administrative Factors: Finally, there were administrative factors that enabled Alexander’s victory, namely his  ability to secure the confidence of the elites he ultimately conquered. This is not an innovation  of the Greek general himself; it was, in fact, a key ingredient in the recipe of success for  the Achaemenid Empire. Alexander’s success was in taking these tactics, as well as other Achaemenid  administrative institutions, and using them to his advantage. Thus, Alexander was not just  relying on propaganda to conquer the Persians, but building and adapting networks with local  elites. For instance, when he conquered Ionia upon his landing in Asia Minor, he restored the  democracies of the city-states but ensured they paid vassalage taxes to him. When he conquered the  core of the Persian Empire in Persepolis and Susa, he tried to engage with and maintain many  satrapal administrative structures. Alexander often innovated by placing Greeks in positions  of authority alongside some Persian satraps, as well as by securing the allegiance of many  Achaemenid nobles at court. This is because the Achaemenid Empire’s political and administrative  core was, according to Rolf Strootman, a large web of social networks which Alexander  understood he needed to insert himself into.

[00:16:44]This combination of continuity and innovation was  key in Alexander securing control over Persia.

[00:16:51]Darius III appears not to have been able to have  an equal level of control over both imperial and local social networks. His uneven control over  the Achaemenid realm was a detriment to his capability to block Alexander from establishing  a springboard in his territory. This allowed the Macedonian to gain additional territories through  the effective use of logistical supply chains. It was also much easier for social elites in Judaea,  Egypt, and parts of Asia Minor to change their allegiance to Alexander. Darius, thus, only had  the core of the Persian elite to side with him.

[00:17:25]He was, however, not able to sustain this support  when he was defeated in battle by Alexander. This weakness may have stemmed from the sheer magnitude  of his defeats, or from his provincial origins as a distant relative of the royal family. Thus,  Darius fled to the east, to the mountains of Bactria and Sogdiana. But his alliance structure  was insecure, and the satrap-turned-pretender Bessus killed him. The convergence of the previous  military and propaganda factors, as well as the instability of the Persian Empire's background,  made the administrative foundations of Darius’s defence against the Greek invasion rather shaky.  Once they came under the slightest pressure, Darius lost his legitimacy in the eyes of his  fellow nobles. Alexander’s swift capture of those institutions as soon as Darius fled  made any counter-attack highly implausible.

[00:18:17]● Conclusion: In the end, it was a combination of historical factors that allowed for  Alexander’s conquest of Persia. Alexander’s genius was an important part of the equation, but he also  faced a formidable opponent in Darius III. Thus, it was both Alexander’s ability to easily  establish a foothold in Asia Minor and the issues rocking the Persian Empire that gave him  a solid foundation for victory. In addition, Philip’s military reforms and Alexander’s  own strategic capabilities enabled a push into Persia and the Levant. Alexander’s  own diplomatic and administrative skills, along with the use of Achaemenid and Levantine  officials, helped cement Greek rule, and the stunning military victories at Gaugamela, Issus,  and Granicus ultimately cost Darius his power base. Alexander's victory was not inevitable and  was partly due to favourable circumstances. But it was also built on prudent foundations  and Alexander’s own ability to innovate, as well as the reliability of his Companions. More videos on the ancient world are on the way, so make sure you are subscribed and have pressed  the bell button to see it. Please consider liking, subscribing, commenting, and sharing - it  helps immensely. Our patrons and YouTube members can watch more than 200+ exclusive  videos - join their ranks via the link in the description or by pressing the join button  under the video to watch these weekly videos, learn about our schedule, get early access  to our videos, access our private Discord, and much more. This is the Kings and Generals  channel, and we will catch you on the next one.