To some, it’s considered ‘the first Crusade’;
to others, the ‘last Great War of Antiquity’. In 622, after 20 years of war, the Byzantine
Empire was on the brink of destruction, having lost region after region to the Sasanian Persian
Empire and its King, Khosrow II. But over the next 6 years and 4 campaigns,
the Byzantine Emperor Heraclius would not only completely reverse these territorial
losses, but also trigger the downfall of the Persian King himself. Background: Persia Ascendant, 602-622 The final Byzantine-Persian war took place in an increasingly unstable world. In Constantinople, the cash-strapped Byzantines
struggled to meet the demands of mutinous soldiers. In Ctesiphon, the Persian Kings had to fend
off a series of noble revolts. On top of this, migrating peoples were pressing
down from the northern steppes: the Avars and Slavs into the Byzantine Balkans, the
Turks along the Persian shores of the Caspian Sea. In 590 AD, a noble revolt in Persia forced
King Khosrow II to flee to the Byzantines. There, he got the support of Emperor Maurice,
who managed to restore Khosrow to the throne. But Maurice’s price was steep: Persia had
to cede the highlands of historical Armenia to the Byzantines, leaving the Sasanian heartlands
of Mesopotamia and western Iran vulnerable to a future invasion. So when Maurice himself was killed by a military
mutiny in 602, Khosrow swiftly took advantage to declare war under the pretext of avenging
his benefactor. With the Byzantine military in political disarray,
Persia began to reclaim not just Armenia, but also the Byzantine forts shielding Syria
from invasion. In 610, Heraclius became Byzantine Emperor
after another revolt, and the resulting chaos opened the floodgates. One by one, the rich cities of Syria and Egypt
fell to Persian armies: Antioch in 610, Jerusalem in 614, Alexandria in 619. The Byzantines in the East were reduced to
two regions: Anatolia and the Balkans, and even these were being devastated by Persian
and Avar-Slav invasions respectively. Were the Byzantines about to meet the fate
of the Western Roman Empire? Despite the dire situation, the Byzantines
still had a few glimmers of hope. The first lay in the Byzantine army, even
in its sharply reduced and demoralized state. By this time, both Byzantines and Persians
fielded similar armies, being built around a core of professional ‘composite cavalry’
skilled in both horse archery and melee combat. Equipment and tactics largely followed steppe
nomad practice, from the powerful composite bow to the emphasis on feigned retreats and
long-distance pursuits. Still, the Byzantines saw their army as slightly
better-equipped and better-drilled than their Persian counterparts, which gave them the
confidence to risk open battle while the Persians resorted to smaller-scale ambushes instead. But this advantage didn’t mean a lot, given
the sheer disparity in resources between the Byzantines and the Persians: the recent conquests
might have taken away a third of Byzantine revenue, while adding 50% to Persia’s. The good news was that whatever the Byzantines
had left was mostly shielded behind the double walls of Constantinople, or the ‘wooden
wall’ of its Mediterranean fleets. Heraclius’ government squeezed as much as
it could out of this shrunken base: raising taxes and cutting expenses, confiscating local
revenue and Church treasure, not to mention debasing the currency. Any one of these policies could generate significant
unrest, so to justify these actions, Heraclius worked closely with the Church, recasting
the Persian war as a defense of Christianity against the pagans, where present suffering
would be compensated for by spiritual rewards. This partnership must have been effective,
for despite Heraclius’ usurping and disastrous reign so far, he suffered few instances of
revolt and especially military mutiny. By the year 622, both the Byzantines and the
Persians were in a position to consider their new steps in what was now a two-decade-long
war. In particular, it’s not entirely clear why
Persia was still in the war. Khosrow certainly intended to keep his spectacular
gains in Syria and Egypt, where his government was already rebuilding the local administration
and extending religious tolerance to local Christians. But it doesn’t seem like he had similar
plans to annex Anatolia, which remained a see-sawing battleground where Persia mainly
sought to capture and deport local resources. Khosrow also seems to not have built a large
Mediterranean fleet, which would have been necessary to capture Constantinople and establish
a secure hold over Anatolia. It’s possible that Khosrow wanted to preserve
a weak Byzantine remnant as a vassal, but couldn’t tolerate or even negotiate with
Heraclius, a person whom Persian propaganda characterized as a bandit. It’s also possible that plans for further
conquests were being opposed by the nobles of Persia, who resented the financial and
manpower contributions they had to make, and feared that a stronger Khosrow might start
exacting revenge on them. Whatever the reason, Persia was now in the
dangerous position of having a directionless war policy, just as the Byzantines were stabilizing
themselves. On the other side, the Byzantines were forced
by circumstance to have a clearer goal in mind: simply end the war. This was easier said than done since, as mentioned,
Khosrow refused to talk to Heraclius. The old Roman Empire had a way to force peace
under these circumstances – namely, by launching invasions deep into Persian Mesopotamia and
threatening its capital of Ctesiphon. Their preferred route down the Euphrates was
by now too well-fortified for this, not to mention that all the Byzantine forts and staging
areas were currently in Persian hands. Instead, Heraclius chose historical Armenia
and Transcaucasia as his route to threaten the Persian heartlands. This was a far less direct method, and the
highlands and river valleys could easily trap an attacking army, especially when winter
snows blocked the mountain passes. But at least the man-made fortifications could
be bypassed, and the local pastureland would relieve some of the Byzantine cavalry’s
logistical burden. Furthermore, Heraclius’ family had military
experience to the region, if not blood ties, granting him a potential intelligence and
political edge over his Persian counterparts. And lastly, directly across the Caucasus to
the north lay the nomadic confederation of the Turks, longstanding enemies of the Persians
whose military help Heraclius was already looking to enlist. A few adjustments had to be made before the
campaigns could begin. First, in order to reliably outmaneuver the
Persian cavalry, the Byzantine army had to be made even faster, and that meant dropping
much of the baggage train and accepting the possibility that they wouldn’t be able to
communicate with Constantinople for months on end. Secondly, given the stakes, Heraclius would
have to lead the army himself – something no Emperor had done for two centuries – and
trust that the government could manage without his presence. And lastly, the Byzantines would have to make
peace in the Balkans, even if it meant paying a large tribute to the Avars and accepting
the loss of extensive territory to the Slavs. And with those things done, Heraclius and
his army could finally set out on campaign. The First Campaign, 622
In spring 622, Heraclius left Constantinople and rendezvoused with his army in central
Anatolia, which had spent the past several years training and making up for previous
losses. The Emperor probably had 15-20 thousand soldiers
under his command, while the Persians likely had 100 thousand split across Syria, historical
Armenia, and in garrisons. Heraclius’ arrival coincided with another
Persian invasion from Armenia. Similar to what they had done in the past,
Persian vanguards penetrated deep into Anatolia to observe and distract Byzantine defenders,
while the main body began sieging down cities in the rear, this time in the eastern Black
Sea coast. Heraclius refused to be distracted by either
effort. Instead, he rushed east into Armenia, beelining
towards Persian territories in western Iran and Azerbaijan. Now, instead of forcing Heraclius to react
to them, the Persians were forced to react to Heraclius, pulling out of Anatolia to chase
the Emperor and hopefully trap him in the Armenian valleys. In the process, the Byzantine army feigned
a retreat in true nomadic fashion, luring the Persians out in pursuit before wheeling
around to defeat them. With this victory, the arduous Byzantine effort
to raise, maintain and train Heraclius’ army was at least partially vindicated, and
so with winter coming on, the Emperor decided to call it a day and withdrew back to Anatolia,
ending this first campaign. There was also an urgent reason for Heraclius
to return: the Avars had broken the peace in the Balkans, which had to be restored
before any further offensive against Persia could begin. Despite nearly being kidnapped by the Avars
and despite having to pay even more tribute, Heraclius achieved this by spring 624, at
which point he returned to the army in central Anatolia. The Second Campaign, 624-625
Heraclius’ second campaign had two overarching goals. First, the Byzantines had earlier sent an
embassy to the Turks, proposing a joint attack on Persia. The Turks were likely going to agree and Azerbaijan
was likely going to be the target, so the Byzantines needed to go there for better communication
or even a rendezvous. Second, Heraclius had obtained intelligence
indicating that Khosrow II himself was at the palace-temple complex of Adur Gushnasp
in western Iran, personally supervising the training of a new army: this might have been
for a new invasion of Anatolia, or perhaps defensive preparations against the impending
Byzantine-Turk alliance. Either way, Khosrow had placed himself within
range of the Byzantine army, and a successful capture or humiliation of the Persian King
might well end the war in a single stroke. March 624 came and Heraclius again sped into
Armenia, bypassing rather than sieging local and Persian defences. By June, he had crossed the region and was
entering western Iran. Khosrow was taken entirely by surprise: all
he could do was muster a hasty defence out of his second-rate troops, and when that was
defeated, flee south to Mesopotamia. Heraclius desecrated and destroyed Adur Gushnasp,
an act which not only was revenge for the Persian capture of Jerusalem, but also one
designed to maximally discredit Khosrow, especially amongst the nobility of western and northern
Iran who had driven previous revolts against the King. Winter was now setting in, and it was time
to execute the other half of Heraclius’ strategy, which was to head back north – raiding
and pillaging all the while – until the army reached Azerbaijan, where they would
winter, replenish losses by recruiting from the regional population, and hopefully meet
up with the Turks by spring. Instead, what spring 625 brought was news
of three Persian armies converging on Azerbaijan, ordered by an enraged Khosrow to destroy Heraclius
once and for all. To the south, a newly-raised force was moving
north from western Iran. To the northeast, another force under the
conquering general Shahrbaraz blocked the route to the Black Sea. And to the west, another force was moving
across Armenia to deal the killing blow. Heraclius’ army basically mutinied at the
news, with some recent recruits deserting while the rest demanded the Emperor head directly
back to Anatolia. That idea ended quickly once the army realized
that Shahrbaraz’s force was in the way, and Heraclius quickly regained his freedom
to command. Moving away from Anatolia, the Emperor quickly
dispersed the inexperienced southern army and re-entered western Iran, prompting Shahrbaraz
in the northeast to pursue for fear of letting the Byzantines pillage the region again. In his haste, the general let himself be drawn
into open battle with the Byzantine army, which resulted in another defeat, after which
Heraclius engaged the western army and routed it as well. With Persian defences in disarray, the Byzantines
were once again free to devastate western Iran before returning to Azerbaijan and then
withdrawing to Armenia for the winter. The reformed Persian army under Shahrbaraz
followed at a respectful distance, but that didn’t stop Heraclius from inflicting one
last defeat on it before the campaign ended. Over the winter, Heraclius finally received
the news he had waited so long for – the Turks were going to invade Persia next year. But two can play at this game of nomadic chess,
and whatever relief came from this was soon overshadowed by the news that the Avars had
again ended their peace with the Byzantines – probably due to Persian efforts – and were
amassing their largest force yet to assault Constantinople. The Third Campaign, 626
Whatever plans Heraclius had for 626 had to be shelved to deal with the Avars, if only
to prevent the Byzantine capital falling into panic and political chaos. As spring 626 dawned, Heraclius made for central
Anatolia – but not through the direct eastern route. Instead, he went southeast through northern
Syria, likely to observe and disrupt any Persian attempts to militarily support the Avars. Shahrbaraz once again gave chase, but was
ultimately repelled by Heraclius. Now back in friendly territory, the Emperor
had a choice to make: he could go back to Constantinople like in 623, or he could stay
with the army to confront any Persian advance. Heraclius decided to stay, only sending a
small contingent back to support his capital. This reflected his confidence in the upcoming
siege: while the Avars were well-versed in city warfare, Constantinople’s size and
defences were on a completely different level – and even though the Avar army was unprecedented,
their rudimentary logistics meant that they only had a brief window to capture the capital
before their own supplies ran out. Moreover, as the Persians still had not built
a fleet to challenge Byzantine control of the Eastern Mediterranean, there was no way
their armies could cross into Europe to help the Avar assault. In other words, the Emperor’s leadership
and inspirational presence would be much more impactful in battle against the Persians than
it was in resisting the Avar siege. Events validated Heraclius’ decision. The Avars arrived outside Constantinople in
late July, but after a week of hard fighting, they had to retreat due to a lack of supplies. A Persian force under Shahrbaraz indeed appeared
on the coast opposite the Avars, but they were of little significance as the Byzantine
fleet prevented any attempt by the two armies to link up, and eventually the Persians too
withdrew back to Syria. Meanwhile, Heraclius’ army repelled a Persian
attempt to invade western Anatolia, and the Turks erupted into Azerbaijan and western
Iran, devastating those territories for the third time in three years. 626 is sometimes seen as the climax of the
Byzantine-Persian War and a near-death experience for the Byzantines. In reality, it seems more like a desperate
gamble by Khosrow to keep Heraclius away from Persia for a few years, perhaps even force
some sort of panicked coup against him. The King failed on these two counts, and now
faced not just formidable foes across multiple fronts, but also the increasing anger of war-weary
nobles, who were sick of the annual ravaging of their estates and the punishments hurled
at them for failing to defeat Heraclius. General Shahrbaraz, in particular, would keep
his army curiously inactive in Syria for the rest of the war, refusing to act even when
his intervention would have saved his King from what Heraclius had planned for the next
year. The Fourth Campaign, 627-628
With the Avars defeated, the Persians withdrawing and the Turks in the war, the time had finally
come for Heraclius to force peace upon the Persians. For 627, the Turks and Byzantines would jointly
conquer Transcaucasia, breaking through the natural and man-made defenses that shielded
the heartlands of Mesopotamia and western Iran from the steppe nomads. Presumably, the two allies would then thoroughly
devastate the latter until the government at Ctesiphon agreed to peace. The beginning of the campaign went smoothly:
the Byzantines took the Black Sea coast, while the Turks again broke into Azerbaijan. Only the vassal-fortress of Tiflis kept the
two allies apart, but remarkably, it held out against their combined efforts for the
rest of the campaign season. By September, the Turks had to withdraw back
north before the Caucasus passes snowed over, leaving Heraclius with the prospect of a wasted
year where the Persians could rest and recover. At this point, either as a bold gamble, or
with the knowledge that key Persian forces – most notably Shahrbaraz’s army in Syria
– were neutralized, Heraclius decided to finally go for the jugular. Not long after the Turks, the Byzantine army
also began retreating from Tiflis, seemingly ready to head through Armenia and back home. But then Heraclius unexpectedly moved south,
entering western Iran and prompting the local Persian army to pursue. By mid-October the Byzantines had crossed
the mountains separating Iran from Mesopotamia, and now the Emperor was in the Sasanian heartland,
the center of Khosrow II’s government and prestige. An urgent Persian attack on the Byzantine
army near Nineveh was dispersed in November using the familiar tactic of feigned retreat. Only second-rate forces and palace garrisons
now stood between Heraclius and Khosrow, and at this point the Persian government fell
into a panic. Khosrow fled to Ctesiphon, ordered a purge
of disloyal nobles, and began seizing whatever was within his grasp to defend the capital. All the while Heraclius was moving south,
pillaging the noble estates, destroying the royal palaces, and publicly threatening to do it
all over again next year with the Turks alongside him. That said, the irrigated terrain of Mesopotamia
was not ideal for Byzantine cavalry, and Ctesiphon even in its current state was a bit too formidable
for Heraclius’ liking. So in January 628, the Byzantines turned and
made the long trek back north. This was of no help to Khosrow – a group
of nobles would overthrow and execute him the next month, beginning a period of political chaos that
would see 11 Kings crowned over the next 6 years. Taking advantage of Persia’s instability,
Heraclius would reverse all of Khosrow’s conquests by 630, restoring Syria and Egypt
to the Byzantines just as a new threat loomed from the Arabian Desert. Conclusion
Heraclius’ campaigns are an example of an indirect approach to war strategy. In the quest to defend Byzantine Anatolia
and obtain peace with the conquering Persian Empire, Heraclius did not set out to destroy
Persian armies nor to retake captured cities, which were not fights he could win given the
disparity between Byzantine and Persian resources. Instead, by threatening and pillaging core
Persian territories, Heraclius repeatedly engineered the withdrawal of invading Persian
armies and promoted war-weariness amongst its nobility. This eventually led to political chaos within
Persia’s government, which in turn allowed the Byzantines to reclaim Syria and Egypt
without having to fight in those territories. And although Heraclius’ gains would be swiftly
lost, the method by which they were achieved would remain a point of pride in Byzantine
military history, and influence their strategy in their wars against the Muslim Arabs.
