Rome vs Persia: An Unwinnable War

What is discussed, and when

1. 0:00 – 3:00: C.R. Whittaker, Ctesiphon, Edward Luttwak, John Mann
2. 3:00 – 6:00: C.R. Whittaker, Velleius Paterculus
3. 6:00 – 9:00: Mithridates, Euphrates, Tigris
4. 9:00 – 12:00: Trajan, Parthian Empire, Ctesiphon, Euphrates
5. 12:00 – 15:00: Trajan, Parthian Empire, Ctesiphon, Lucius Verus
6. 15:00 – 18:00: Ardashir, Ctesiphon, Lucius Verus, Palmyra

Notable quotes from "Rome vs Persia: An Unwinnable War"

• Circumstances that shaped this long frontier, and why Rome and Persia became eternal enemies. The question of why the Roman frontier stopped where it did has been asked by many…

  about Edward Luttwak · at 0:41

• Ultimately failed to consider the numerous other factors that contributed to the halt in Rome’s territorial expansion, as well as the fundamental logistical, geographical, and…

  about C.R. Whittaker · at 4:16

• Process of assimilation was indirect and took much longer than direct military conquest. The progress that Rome made in maintaining its soft power over these client states was…

  about Mithridates · at 6:44

• Conversely, the Parthians also utilized a similar series of relationships with client kingdoms based on the earlier Seleucid model of governance. They relied on the Tigris and…

  about Euphrates · at 7:54

• This raises another question: why was Trajan’s campaign different? In 114 AD, Emperor Trajan led Roman armies deeper into Persia than they had ever done before, ultimately…

  about Trajan · at 9:13

• The economic reality of conquest also limited both powers’ ability to meaningfully campaign deep into either state’s territory. While we have excellent figures on the size and…

  about Parthian Empire · at 11:02

• Power of the Parthian Empire. Unlike Alexander's campaigns against their Achaemenid Persian predecessors, the Parthians were not decisively defeated in multiple set-piece…

  about Lucius Verus · at 14:02

• The available sources. Still, the influence of Palmyra and Characene in the civil war, combined with the Roman annexation of Osrhoene and parts of Armenia, weakened the…

  about Ardashir · at 15:34

Who and what is mentioned in this episode?

People

• Trajan — Person · Referenced historical figure (Roman emperor) · 5 mentions · first at 9:13
  Used as the key case study for why Rome’s eastern frontier could be pushed temporarily (114 AD campaign) but not held permanently.
• C.R. Whittaker — Person · Referenced expert (modern historian) · 2 mentions · first at 2:01
  Provides the episode’s preferred explanatory framework: frontiers as zones/peripheries shaped by logistics, economy, and local tolerance rather than hard borders.
• Lucius Verus — Person · Referenced historical figure (Roman emperor/co-emperor) · 2 mentions · first at 14:13
  Cited as Trajan’s later counterpart who also campaigned successfully to Ctesiphon, illustrating that taking the Parthian capital did not equal conquest.
• Edward Luttwak — Person · Referenced expert (modern historian/strategist) · 1 mention · first at 1:50
  Presented as the best-known earlier interpreter of Roman frontiers (grand strategy/ideology), whose view the episode frames as dated and contested.
• Ardashir — Person · Referenced historical figure (founder of Sasanian dynasty) · 1 mention · first at 15:43
  Explains the transition from Parthian (Arsacid) to Sasanian power: Roman pressure and regional politics created an opening for his rise and later Sasanian centralization.
• Mithridates — Person · Referenced historical figure (regional rival king) · 1 mention · first at 6:55
  Serves as an example of a powerful Near Eastern rival (Pontic Empire) that disrupted Rome’s client-state influence and frontier management in the Late Republic.
• Velleius Paterculus — Person · Referenced ancient source (Roman historian) · 1 mention · first at 3:08
  Used as evidence for Roman geographic misunderstanding (Elbe–Rhine distance), supporting the argument that ancient borders weren’t ‘scientific’ hard lines.
  While the ancient commentators Appian and Strabo both claim that England was not worth the expense of conquest, as it had little economic value, the Romans conquered it anyway…
• John Mann — Person · Referenced scholar (critic of Luttwak, per episode) · 1 mention · first at 2:01
  Named as an early challenger to Luttwak’s frontier thesis, helping establish the historiographical debate the episode summarizes.
  Many prior historians. The most well-known of these works belongs to Edward Luttwak, who saw the frontier as the failure of the Roman regime’s ideology and grand strategy.…

Concepts & topics

• Parthian Empire — Concept · 2 mentions · first at 11:13
• Sasanid dynasty — Concept · 1 mention · first at 15:53
  Weakened the position of Parthian King Vologases VI and created an opening for Ardashir’s rise in the ensuing civil war. Ultimately, this division created an opportunity for…
• Seleukid state — Concept · 1 mention · first at 11:24
  Which were hideously expensive, data on the Parthian Empire and its economy is comparatively limited. The size and geographic span of the Parthian Empire, throughout its…

Places & events

• Ctesiphon — Place · 4 mentions · first at 0:18
  This raises another question: why was Trajan’s campaign different? In 114 AD, Emperor Trajan led Roman armies deeper into Persia than they had ever done before, ultimately…
• Euphrates — Place · 3 mentions · first at 7:59
• Tigris — Place · 2 mentions · first at 7:59
  Conversely, the Parthians also utilized a similar series of relationships with client kingdoms based on the earlier Seleucid model of governance. They relied on the Tigris and…
• Palmyra — Place · 2 mentions · first at 10:17
  Significantly expand its frontier further into Parthian territory after a second campaign and sacking of Ctesiphon under Lucius Verus. With a new frontier at Nisibis and Dura…

Full transcript with timestamps

0:06 The historic rivalry between the Roman Empire and the various iterations of the Persian Empire is one of the most bitter, bloody and enduring feuds in world history. Spanning over nearly 700 years, the spectacularly brutal battles of Carrhae, Rhandeia, and Ctesiphon are just a few of the long list of conflicts between Rome and Persia over nearly three centuries. But why did great Roman leaders like Crassus or Antony fail to conquer Persia, where Alexander the Great and his Macedonian Phalanxes had succeeded in previous centuries? In this episode, we’ll delve into the geopolitical and socioeconomic circumstances that shaped this long frontier, and why Rome and Persia became “eternal enemies.”

1:46 The question of why the Roman frontier stopped where it did has been asked by many prior historians. The most well-known of these works belongs to Edward Luttwak, who saw the frontier as the failure of the Roman regime’s ideology and grand strategy. Luttwak’s view is now heavily dated, having been first contested by historians John Mann and later by C.R. Whittaker. To understand why Rome’s frontier with Parthian Persia and later Sasanian Persia ended where it did, it is necessary to explain what a frontier meant to the Romans in the first place.

2:18 When depicted on most modern maps, the borders of the Roman Empire at its greatest extent look solidly defined. However, the modern concept of a border as a strict boundary between states effectively did not exist as a concept in the Ancient World. To the Romans, there were merely limits to their control or authority. The limites or “limits”, which today define the Roman frontier, were not hard lines, but zones of control that unified a region where multiple cultures met and interacted. The Romans had no “scientific” concept of a border or why they ended a border where they did.

2:53 Part of this was due to the fact that the Romans simply lacked accurate information. For example, while the ancient commentators Appian and Strabo both claim that England was not worth the expense of conquest, as it had little economic value, the Romans conquered it anyway and found it to be rich in minerals. The Roman senator Velleius Paterculus claimed that Emperor Tiberius thought the Elbe was 400 miles from the Rhine, when it was a mere 200 to 250 miles, and this was his knowledge from after his campaign in the region was over! Hard geographic or cultural borders were lacking both in reality and conceptually. Roman fortresses and markets were built on both sides of the Rhine and Danube. Strabo mentions Roman client rulers outside of Rome’s borders, and Procopius mentions Roman landowners and workers who regularly crossed between Roman and Sasanian control. Long frontiers, such as Africa and the Levant, featured significant distances between the

3:49 forward walls and posts that controlled trade and the actual military frontier. The lines of fortifications were primarily for defending roads, rather than delineating the limit of Roman power. Why then did the Romans stop where they did? Luttwak posited that the borders existed because they represented the milestone at which the grand Imperial ambitions of the Roman state began failing due to political and military turbulence within the Empire. This view ultimately failed to consider the numerous other factors that contributed to the halt in Rome’s territorial expansion, as well as the fundamental logistical, geographical, and economic challenges faced by the empire. These were the arguments posited by Historian C.R. Whittaker, who asserted that fundamentally, Rome’s border with Persia reached an equilibrium in which the Empire was large enough to prosper and project power, without antagonizing the intersecting peoples that made up

4:42 this zone. This zone, therefore, also defined the geography and environment in which it could exist, only as far from the core as the economic and logistical engine could sustain. In the world of Roman frontier studies, this is known as the periphery, divided into the inner and outer frontiers. This inner frontier was the point at which the Empire could reliably supply and operate an army and its administration within the limits of the local population’s tolerance. In contrast, the outer frontier was the wider operating range in which the Empire could exert its political and military power, but whose presence would not be tolerated in the long-term.

5:20 Thus, the stabilization of the Roman frontier begins to make sense in this context. Roman naval power made supporting the movement of armies along the Mediterranean coast relatively simple due to the stark contrast between the rapidity and costs of overland and seaborne logistics. Rome’s major campaigns into Gaul, Germania, and Spain could all be supported by supply routes upstream along rivers like the Rhone or the Elbe, with dredging, widening, and canal projects frequently attested to enable or maintain such logistical chains. However, many regions lack traversable rivers, particularly in the East Mediterranean. This presents a twofold problem, as the geography limits Rome’s ability both to conquer and to extract resources or economic value from the region. In this sector, as well as in Armenia, the Romans secured the fealty of local rulers, utilizing native client Kings to exert their power over the region without

6:15 the intolerable and unsustainable presence of an army in a distant or isolated region. The Romans and the client polity established a series of political, social, and economic relationships, albeit thus forming part of the outer frontier or periphery. Gradual integration was facilitated by these relationships, which enabled Rome to expand its frontier and establish direct administrative control as local political conditions evolved in their favor over time. The tradeoff was that the process of assimilation was indirect and took much longer than direct military conquest. The progress that Rome made in maintaining its soft power over these client states was hindered only by the emergence of powerful rivals in the region, such as the Pontic Empire of King Mithridates, which challenged Rome’s political control over the Near East during the Late Republic.

7:05 At its zenith, Roman influence extended far deeper into the East than is reflected in the Roman-Persian border depicted by many modern maps. At the height of their power, the Roman Emperors had a policy of interfering in succession and internal affairs in not just Armenia, but also in Parthia itself. In many ways, effectively all of Armenia, the Caucasus, and West Parthia could have been considered part of Rome’s periphery, and Parthia was even occasionally viewed as a client kingdom of Rome. Their governments, therefore, sought to justify this relationship, with the royal Arsacid dynasty of Persia providing hostages to be raised by the Julio-Claudians as if they were royal foster parents, and the Romans using those hostages to claim imperial dominance over all of Parthia, even enthroning several as Shahanshah, or the Persian King of Kings.

7:54 Conversely, the Parthians also utilized a similar series of relationships with client kingdoms based on the earlier Seleucid model of governance. They relied on the Tigris and Euphrates to assert their authority over the western parts of their empire. The problem was the geographic reality of communication lag, which made extending control through the client relationship impermanent. Logistically, the Tigris and Euphrates were easy to traverse up to the first cataracts, much like the Nile river. This made campaigning along these rivers the logical choice, combined with an abundant local agricultural supply for keeping an army afield. Where the rapids prevented the advance of logistical vessels further upriver, Parthia’s influence waned. The same can be said for Rome, which had to rely on overland routes into the Armenian Plateau when it ventured away from the riverine corridor of Mesopotamia. This is the region where we find small client states,

8:47 such as Osrhoene, Edessa, Commagene, Corduene, Sophene, and Adiabene, in which both Rome and Parthia interfered in local dynastic politics or attempted to shift loyalties. Thus, the border arrived at a natural equilibrium where the spheres of influence of these two polities met, which often maintained flexible arrangements that enabled the kinds of descriptions of this border we find in the writings of ancient authors such as Strabo and Procopius. This raises another question: why was Trajan’s campaign different? In 114 AD, Emperor Trajan led Roman armies deeper into Persia than they had ever done before, ultimately capturing the Parthian Capital of Ctesiphon and possibly reaching the Persian Gulf. The Roman historian Cassius Dio attributes Trajan’s motivations to a desire for prestige and legacy.

9:36 One hypothesis suggested by 20th century historians was the desire to gain access to the trade routes to East Asia as the primary motive for conquest, but this has been broadly rejected by modern ancient economic historians. There is little evidence for firm Parthian control over the eastern trade routes, often collectively termed the “Silk Road,” and Roman sources do not provide any evidence of a defined economic policy towards trade with the far east. Another hypothesis espoused by modern historians is that Roman policy towards Parthia in the second century revolved around establishing a new defensive line along the Khabur river, which would then secure the client kingdoms within the Roman sphere of influence, such as Armenia, from Parthian influence. These historians point towards the ambitions of Palmyra and its close ties with Characene, and the relationship of the Romans with the Arab peoples who controlled

10:27 both sides of the Euphrates, as evidence for this political vision for the region. Ultimately, Trajan was unable to overpower or sway every ruler necessary to permanently extend the frontier, as client polities like Hatra, Elymais, and Atropatene remained opposed to Roman occupation. The overstretching of the Roman periphery is evident in the revolts that led to the abrupt end of Trajan’s campaign, as Roman garrisons in Mesopotamia were ejected from the cities, and populations in Syria and the Levant began to rise up in opposition to the economic burden placed upon them.

11:02 The economic reality of conquest also limited both powers’ ability to meaningfully campaign deep into either state’s territory. While we have excellent figures on the size and costs of Roman campaigns, which were hideously expensive, data on the Parthian Empire and its economy is comparatively limited. The size and geographic span of the Parthian Empire, throughout its rivalry with Rome, was broadly similar to that of the Hellenistic Seleukid state prior, from which they drew many of their governing and economic institutions. Historian Michael J. Taylor estimates the revenues of the Seleukid state at approximately 50 to 60 million bronze Drakhmai at its apex, which would likely be comparable to Parthian revenues. However the state’s expenditures were evidently quite high: Roman sources suggest that the Parthians could field large armies of anywhere from 10,000 to 50,000 men, which on the upper end is comparable

11:54 to Antiochus III’s force at Magnesia, an army for which Taylor estimates the total campaign expenditures at around 100% to 125% of the Seleukids’ revenue. Of this, he estimates that food and logistics cost around 10 million Drakhmai, supplied by a fleet that requires approximately 15 million Drakhmai to maintain, a force the Parthians fundamentally lacked in the Mediterranean. The point of this number is to show the difficulty of campaigning deep into territory that was technically within or near to the territory of Antiochus’ own polity, much less the problems and expenses associated with campaigning deep into a foreign polity.

12:32 Extracting and maintaining a standing army in the region was also challenging for the Seleukids and Parthians. The forces required to occupy a region consumed a significant portion of their total revenues, as evidenced by the number needed to subdue Caucasian Albania under Vologases I. Finally, while the decentralized organization of the Parthian realm made it resilient, it also limited its ability to increase direct administrative control across much of its periphery and, therefore, mount large-scale offensive campaigns further west into Roman territory.

13:04 In contrast to the Parthians, who were certainly formidable as a political and economic power, the Romans had an economic engine that vastly outclassed any other neighbouring polity, except for their far-off peers in Han China. Masters of logistics, the Romans would spend months or even years preparing for a major incursion into enemy territory, as seen, for example, in the lead-up to Trajan’s campaign, where logistical preparations for the operation had already begun three years in advance and encompassed all of Anatolia in the effort. The Tigris and the Euphrates enabled the Romans to campaign downstream, provided they could transport supplies over the Nur and Southeastern Taurus mountains to the river plains beyond. Riverine access, combined with the Parthians’ choice of capital at Ctesiphon on the Tigris, made this corridor the logical choice to campaign against their foe, but it would not result in the Parthians’ conquest.

13:57 The problem was that taking the Parthian capital of Ctesiphon fundamentally did not cripple the power of the Parthian Empire. Unlike Alexander's campaigns against their Achaemenid Persian predecessors, the Parthians were not decisively defeated in multiple set-piece battles to weaken their legitimacy by Trajan or his successor, Emperor Lucius Verus. Furthermore, the Parthian administration was much more decentralized, able to fall back on its other seats of power at Nisa and Hekatompylos. Foraying deeper into Persia would also involve moving supplies through the passes of the Zagros Mountains into the Central Iranian Plateau, a much more daunting affair than campaigning into the Armenian Highlands. This was beyond even the Romans’ considerable logistical capability, and much like Alexander’s army beforehand, Trajan’s armies would have been left starved of water or would have frozen to death along the mountain passes. Finally, neither

14:51 Trajan nor Verus had either circumstantial or systemic politics within their opponents’ polity working in their favour across the rest of their periphery, unlike with Darius III and Alexander. Rome would never succeed in achieving such a sweeping conquest, but ultimately did manage to significantly expand its frontier further into Parthian territory after a second campaign and sacking of Ctesiphon under Lucius Verus. With a new frontier at Nisibis and Dura Europos, Roman influence had shifted the equilibrium further East, likely enabled by the rise in power of Palmyra and its political allies. Whether or not this contributed to the destabilization of Arsacid rule and the eventual collapse of the Parthians is impossible to say based on the available sources. Still, the influence of Palmyra and Characene in the civil war, combined with the Roman annexation of Osrhoene and parts of Armenia,

15:43 weakened the position of Parthian King Vologases VI and created an opening for Ardashir’s rise in the ensuing civil war. Ultimately, this division created an opportunity for the Sasanid dynasty to centralize the government and build a more effective governing apparatus, as many of the client kingdoms were permanently subsumed into an administrative and logistical backbone that allowed them to push back against the Roman frontier that had shifted Eastwards, enabling a campaign that reached over the Nur Mountains to sack Antioch in 253.

16:13 The Sasanian War of 602-628 saw the even more organized and centralized Sasanian polity able to exploit Roman civil war and push through the frontier into the Roman core as far as Egypt and Anatolia. However, their control over any of these regions in this period was tenuous at best. The expansion of the periphery into the Mediterranean destabilized the Sasanian house and allowed internal politics to restore the previous equilibrium, at least until the emergence of the nascent Islamic Caliphate some decades later.

16:45 The question, therefore, is, given the economics, logistics and military resources, could the Roman Empire have conquered Persia? The answer to that is: yes. Of course, it could have. If you give one side all of the advantages necessary to do it, then the thought experiment becomes pointless, because it would happen. The factors that enabled the Parthians and Romans to defeat each other and shift the balance of power rarely had anything to do with battles and victories, but rather everything to do with the political, economic, and societal circumstances surrounding the campaigns. Rome and Persia were therefore “eternal enemies” not because they could not defeat each other, but because that equilibrium was the natural solution for the geography, economy, and people of the frontier.

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Questions about this episode

What is discussed in "Rome vs Persia: An Unwinnable War"?

In order: 0:00 C.R. Whittaker, Ctesiphon, Edward Luttwak, John Mann; 3:00 C.R. Whittaker, Velleius Paterculus; 6:00 Mithridates, Euphrates, Tigris; 9:00 Trajan, Parthian Empire, Ctesiphon, Euphrates; 12:00 Trajan, Parthian Empire, Ctesiphon, Lucius Verus; 15:00 Ardashir, Ctesiphon, Lucius Verus, Palmyra.

What is mentioned in this Kings and Generals episode?

15 people, works and ideas are mentioned, including Trajan, C.R. Whittaker, Parthian Empire, Ctesiphon, Lucius Verus, Edward Luttwak. Each one on this page links to its own page with every episode that mentions it.

How long is "Rome vs Persia: An Unwinnable War"?

The episode runs 18 min; the transcript is about 2,807 words in 23 timestamped sections.

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