Byzantine – Sasanian wars The Byzantine – Sassanid wars , also known as the Irano - Byzantine wars refers to a series of conflicts between the Eastern Roman ( Byzantine ) Empire and the Sassanid dynasty of the Persian Empire . A continuation of the Roman - Persian War s , the conflict involved several smaller campaigns and peace treaties lasting for years at a time . Strategy and tactics . Romans . Roman strategy . The Roman Empire had reached its greatest extent under the Emperor Trajan . However , before Trajan , the Emperor Augustus set about stabilizing the frontiers of the Empire . As a result , the Romans were more interested in simply defending their territory and consolidating the Empire rather than in attempting to conquer Persia . Roman tactics . The Romans employed the best infantry of the time : heavily armed and armoured soldiers plus numerous auxiliaries . By the 4th century A . D . , armour was less often used , and by the 5th century , Germanic mercenaries were employed . The Romans continued to use heavy infantry of the legionary type , but these were ineffective against the mobile Persian horse archers . From the 3rd century heavy cataphract cavalry wearing full horse and rider armour became an increasingly important component of Roman armies . Persians . Sassanid strategy . The Sassanid dynasty had a more or less secure northern and eastern border due to the mountainous terrain of Middle Asia and Afghanistan . The Western border was determined by Sassanid control of Mesopotamia . Due to the flat nature of the land , it was easy to overrun and difficult to defend . With these natural boundaries , the Sassanid Persians had only Westward to expand . The Sassanids were becoming as efficient in siege warfare as the Romans , capturing and sacking a number of cities as part of a larger goal of exacting tribute and land from the Romans . However , the nature of the warfare was one of attrition with heavy casualties on both sides . As a result , little land was exchanged between the two powers ; rather , vassal states and tribute would have been demanded . Sassanid tactics . The Sassanid Persians employed cavalry archers and heavy cataphracts to counter the heavy Roman infantry . In battle , these archers proved their worth until the Romans began to adopt similar methods of warfare . Rise of the Sassanid dynasty . Following Trajan ' s successful conquest of Mesopotamia in the 2nd century , the Parthian dynasty began to decline . Ctesiphon was overrun by the Romans but the lack of any permanent establishment meant that the Sassanid dynasty filled the power vacuum in the region and started a new Persian Empire in 224 . The Sassanids were a more aggressive enemy than their Parthian predecessors and consequently , the Romans found themselves fighting a more dangerous Eastern opponent at a time when the Roman Empire was weakening due to the civil chaos arising from the death of the Roman Emperor Commodus . Early Roman - Sassanid conflicts . Persian - Roman conflict was renewed shortly after the overthrowing of the Parthian rule and the foundation of the Sassanid empire by Ardashir I ( 226 – 241 ) , who raided in Mesopotamia and Syria in 230 , demanding the restitution of the Achaemenid possessions in Europe . After fruitless negotiations , Alexander Severus set out against Ardashir in 232 ; one column of his army marched successfully into Armenia , while two other columns operated to the south and failed , mostly on account of physical hardship . In any case Ardashir was repulsed and Alexander Severus celebrated a triumph in Rome . In 238 - 240 , towards the end of his reign , Ardashir attacked again , taking several cities in Syria and Mesopotamia , including Carrhae , Nisibis and Hatra . The struggle resumed and intensified under Ardashir ' s successor Shapur I ; he invaded Mesopotamia but his forces were defeated at a battle near Resaena in 243 ; Carrhae and Nisibis were retaken by the Romans . Encouraged by this success , the emperor Gordian III advanced down the Euphrates but was defeated near Ctesiphon in the Battle of Misiche in 244 . Gordian either died in the battle or was murdered by his own men ; Philip became emperor , and paid 500 , 000 denarii to the Persians . In the early 250s , Philip was involved in a struggle over the control of Armenia . Shapur had the Armenian king murdered , and re - opened hostilities against Rome ; he defeated the Roman troops at the Battle of Barbalissos , and then probably took and plundered Antioch . Some time between 258 and 260 , Shapur captured the emperor Valerian after crushing his army at the Battle of Edessa , but his subsequent advance into Anatolia ended , when Odaenathus , the ruler of Palmyra , attacked detachments of the Persians , causing them to retreat to their homeland . In 275 and 282 Aurelian and Probus respectively planned to invade Persia , but they were both murdered before they were able to fulfill their plans . In 283 the emperor Carus launched a successful invasion of Persia , sacking its capital , Ctesiphon ; they would probably have extended their conquests , if Carus had not died in December of the same year . After a brief period of peace during Diocletian ' s early reign , Narseh renewed hostilities with the Romans invading Armenia , and defeated Galerius not far from Carrhae in 296 or 297 . However , in 298 Galerius defeated Narseh at the Battle of Satala , sacked the capital Ctesiphon and captured the Persian treasury and royal harem . The Roman victory was the most decisive for many decades : many cities east of the Tigris were given to the Romans including Tigranokert , Saird , Martyropolis , Balalesa , Moxos , Daudia , and Arzan . Also , control of Armenia was given to the Romans . The arrangements of 299 proved long - lasting . It was Shapur II who broke the long peace between the two empires in mid 330s , and mounted a series of offensives against the Romans with little lasting effect . Shapur launched a new campaign in 359 , successfully laying siege to Amida , and provoked a major offensive in 363 by the Roman Emperor Julian . Despite victory at the Battle of Ctesiphon , Julian was unable to take the Persian capital . He was killed the same year at the Battle of Samarra , during a difficult retreat along the Tigris . His successor Jovian found his army in a disadvantageous position , and was forced to hand over the former Roman possessions east of the Tigris , as well as Nisiris and Singara ; Armenia was also abandoned by the Romans , and was soon conquered by Shapur . In 383 or 384 Armenia again became a bone of contention between the Roman and the Sassanid empires , but hostilities did not occur . With both empires preoccupied by barbarian threats from the north , a largely peaceful period followed , interrupted only by two brief wars , the first in 421 - 422 after Bahram V persecuted high - ranking Persian officials who had converted to Christianity , and the second in 440 , when Yazdegerd II raided Roman Armenia . Anastasian War . The Anastasian War ended the longest period of peace the two powers ever enjoyed . It broke out when the Roman emperor Anastasius I refused to provide financial support to the Persian king , Kavadh I , who tried to gain the money by force . In 502 Kavadh quickly captured the unprepared city of Theodosiopolis , and then besieged the fortress - city of Amida through the autumn and winter ( 502 - 503 ) . The siege of the city proved to be a far more difficult enterprise than Kavadh expected ; the defenders repelled the Persian assaults for three months before the defenders were finally beaten . In 503 the Romans attempted an ultimately unsuccessful siege of the Persian - held Amida while Kavadh invaded Osroene , and laid siege to Edessa with the same results . Finally in 504 , the Romans gained the upper hand with the renewed investment of Amida , leading to the hand - over of the city . That year an armistice was agreed to as a result of an invasion of Armenia by the Hun s from the Caucasus . Negotiations between the two powers took place , but such was their distrust that in 506 the Romans , suspecting treachery , seized the Persian officials . Once released , the Persians preferred to stay in Nisibis . In November , 506 , a treaty was finally agreed upon , but little is known of what the terms of the treaty were . Procopius states that peace was agreed for seven years , and it is likely that some payments was made to the Persians . In 505 Anastasius ordered the building of a great fortified city at Dara . The dilapidated fortifications were also upgraded at Edessa , Batnac and Amida . Although no further large - scale conflict took place during Anastasius ' reign , tensions continued , especially while work continued at Dara . This construction project was to become a key component of the Roman defenses , and also a lasting source of controversy with the Persians , who complained that it violated the treaty of 422 , by which both empires had agreed not to establish new fortifications in the frontier zone . Anastasius , however , pursued the project , and the walls were completed by 507 / 508 . Iberian War . In 524 / 525 Kavadh proposed to Justin I to adopt his son , Khosrau . The proposal was initially greeted with enthusiasm by the Roman emperor and his nephew , Justinian , but Justin ' s " quaestor " , Proculus , opposed the move . Despite the final breakdown of the negotiations , it was not until 530 that full - scale warfare on the main eastern frontier broke out . In the intervening years , the two sides preferred to wage war by proxy , through Arab allies in the south and Huns in the north . Tensions between the two powers were further heightened by the defection of the Iberian king Gourgen to the Romans : in 524 / 525 the Iberians rose in revolt against Persia , following the example of the neighboring Christian kingdom of Lazica , and the Romans recruited Huns from the north of the Caucasus to assist them . By 526 - 527 , overt fighting between the two empires had broken out in the Transcaucasus region and upper Mesopotamia . At the same time , the Persians continued to exert pressure on the Romans to obtain funds from them . The early years of war favored the Persians : by 527 the Iberian revolt had been crushed , a Roman offensive against Nisibis and Thebetha in that year was unsuccessful and forces trying to fortify Thannuris and Melabasa were prevented from doing so by Persian attacks . Attempting to remedy the deficiencies revealed by these Persian successes , the new Roman emperor , Justinian I , reorganized the eastern armies . In 528 Belisarius tried unsuccessfully to protect Roman workers in Thannuris , undertaking the construction of a fort right on the frontier . Damaging raids on Syria by the Lakhmids in 529 encouraged Justinian to strengthen his own Arab allies , helping the Ghassanid leader Al - Harith ibn Jabalah turn a loose coalition into a coherent kingdom . In 530 the Romans defeated the Persian troops at Dara and Satala . In 531 Belisarius was defeated by Persian and Lakhmid forces at the Battle of Callinicum , but , during the summer of the same year , the Romans captured some forts in Armenia , and effectively repulsed the Persian offensive . Immediately after the Roman failure at Callinicum , which resulted in the dismissal of Belisarius , unsuccessful negotiations between Justinian ' s envoy , Hermogenes , and Kavadh took place . Justinian then took steps to bolster the Roman position , trying , at the same time , to engage Kavadh diplomatically . In spring 532 negotiations re - opened between the Roman envoys and the new Persian king , Khosrau I , who needed to secure his own position . The two sides finally came to an agreement , and the Eternal Peace , which lasted less than eight years , was signed in September 532 . Both powers agreed to return all occupied territories and the Romans to make a one - off payment of 110 " centenaria " ( 11 , 000 lbs of gold ) . The Romans recovered the Lazic forts , and Iberia remained in Persian hands , but the Iberians who had left their country were allowed to either remain in Roman territory or return to their native land . Ascendancy of Khosrau I . The successful campaigns of Belisarius in the west encouraged the Persians to return to war , both taking advantage of Roman preoccupation elsewhere and seeking to check the expansion of Roman territory and resources . In 539 the resumption of hostilities was foreshadowed by a Lakhmid raid led by al - Mundhir IV , which was defeated by the Ghassanids under al - Harith ibn Jabalah . In 540 , the Persians broke the " Treaty of Eternal Peace " and Khosrau I invaded Syria , destroying the great city of Antioch and deporting its population to Persia ; as he withdrew , he extorted large sums of money from the cities of Syria and Mesopotamia and systematically looted the key cities . In 541 he invaded Lazica in the north . Belisarius was quickly recalled by Justinian to the East to deal with the Persian threat , while the Ostrogoths in Italy , who were in touch with the Persian King , launched a counter - attack under Totila . Belisarius took the field and waged an inconclusive campaign against Nisibis in 541 . In the same year Lazica switched its allegiance to Persia and Khosrau led an army to secure the kingdom . In 542 Khosrau launched another offensive in Mesopotamia , and unsuccessfully attempted to capture Sergiopolis . He soon withdrew in the face of an army under Belisarius , en route sacking the city of Callinicum . Attacks on a number of Roman cities were repulsed and the Persian general Mihr - Mihroe was defeated and captured at Dara by John Troglita . In 543 , the Romans fielded a force of 30 , 000 troops commanded by the " magister militum " of the East , Martin , for an invasion of Persian - controlled Armenia . They launched an offensive against Dvin , but were defeated by a small Persian force at Anglon . In 544 Khosrau besieged Edessa without success and was eventually bought off by the defenders . The Edessenes paid five " centenaria " to Khosrau , and the Persians departed after nearly two months . In the wake of the Persian retreat , two Roman envoys , the newly appointed magister militum , Constantinus , and Sergius proceeded to Ctesiphon to arrange a truce with Khosrau . A five - year truce was agreed in 545 , secured by Roman payments to the Persians . Lazic War . In early 548 AD , king Gubaz of Lazica , having found Persian protection oppressive , asked Justinian to restore the Roman protectorate . The emperor seized the chance , and in 548 / 549 AD combined Roman and Lazic forces under Gubaz and the magister militum of Armenia Dagistheus won a series of victories against Persian armies under Mihr - Mihroe and Khorianes , but failed in repeated attempts to take the fort of Petra . In 551 AD , general Bassas who replaced Dagistheus put Abasgia and the rest of Lazica under control , and finally subjected Petra , demolishing its fortifications . In the same year , however , a Persian army under Mihr - Mihroe but was defeated with heavy losses . That year the truce which had been established in 545 AD was renewed outside Lazica for a further five years , with the Romans paying 2 , 000 lbs of gold each year . The Romans failed to completely expel the Sassanids from Lazica , and in 554 AD Mihr - Mihroe launched a new attack , and captured the fortress of Telephis , which was commanded by general Martin . In 557 AD Khusro , who had now to deal with the White Huns , dispatched his envoy Izedh Gushnap to Constantinople and renewed the truce , this time without excluding Lazica , where they kept only a toehold ; negotiations continued for a definite peace treaty . Finally , in 561 AD , Justinian ' s envoy , Peter the Patrician , and Izedh Gushnap put together a 50 - year peace . The Persians agreed to evacuate Lazica , and received an annual subsidy of 30 , 000 " nomismata " annually . Both sides agreed not to build new fortifications near the frontier and to ease restrictions on diplomacy and trade between the two empires . War for the Caucasus . The war began , when the Armenians revolted against Sassanid rule in early 572 AD . Justin II took them under his protection , and sent his nephew , Marcian , against the Persians . Roman troops raided Arzanene , and invaded Persian Mesopotamia , defeating its local forces . Marcian ' s sudden dismissal , however , and the arrival of troops under Khosrau resulted in the ravaging of Syria , the failure of the Roman siege of Nisibis , and the fall of Dara . At a cost of 45 , 000 " solidi " a one - year truce ( later in the year extended to five years ) was arranged , though the Persians still wanted to restore control in Armenia . In 576 AD Khosrau I attempted to combine aggression in Armenia with discussion of a permanent peace . He failed however to take Theodosiopolis , and after a confrontation near Melitene the Persian royal baggage was captured ; there were severe Persian losses either in set battle or during a disorganized fleet over the Euphrates . The Romans exploited Persian disarray by invading deep into Persian territory , raiding Atropatene . Persian confidence revived , when Tamkhusro defeated Justinian in Persian Armenia , where Roman actions had alienated local inhabitants . In the spring of 578 AD the Persians raided Byzantine Mesopotamia ; the Roman general Maurice retaliated by invading Arzanene ; he also took and garrisoned the stronghold of Aphumon , and sacked Singara in Persian Mesopotamia . Khosrau I died early the next year , defeated after so many victories . During the 580s the war continued in inconclusive fashion , with victories on both sides . In 582 AD Maurice defeated Tamkhusro , who was killed , but the Roman general did not follow up his victory ; he had to hurry to Constantinople to pursue his imperial ambitions . In 589 AD the Persians achieved a last success , capturing Martyropolis through treachery , but in the same year the stalemate was shattered when the Persian general Bahram Chobin , having been dismissed and humiliated by Hormizd IV , raised a rebellion . Hormizd was overthrown in a palace coup in 590 AD and replaced by his son Khosrau II , but Bahram pressed on with his revolt regardless and the defeated Khosrau was soon forced to flee for safety to Roman territory , while Bahram took the throne as Bahram VI . With support from Maurice , Khosrau raised a rebellion against Bahram , and in 591 AD the combined forces of his supporters and the Romans defeated Bahram , restoring Khosrau II to power and bringing the war to an end . In exchange for their help , Khosrau not only returned Dara and Martyropolis but also agreed to cede the western half of Iberia and more than half of Persian Armenia to the Romans . Climax . During Maurice ' s Balkan campaigns , he and his family were murdered by Phocas in November 602 after a mutiny . Khosrau II seized this opportunity to attack the Roman Empire and reconquer the Roman province of Mesopotamia . The war initially went the Persians ' way , partly because of Phocas ' brutal repression and the succession crisis that ensued as the general Heraclius sent his nephew Nicetas to attack Egypt , enabling his son Heraclius the younger to claim the throne in 610 . Phocas , an unpopular ruler who is invariably described in Byzantine sources as a " tyrant " , was eventually deposed by Heraclius , who sailed to Constantinople from Carthage with an icon affixed to the prow of his ship . By this time the Persians had conquered Mesopotamia and the Caucasus , and in 611 they overran Syria and entered Anatolia . A major counter - attack led by Heraclius two years later was decisively defeated outside Antioch by Shahrbaraz and Shahin and the Roman position collapsed ; the Persians devastated parts of Asia Minor , and captured Chalcedon on the Bosporus . Over the following decade the Persians were able to conquer Palestine and Egypt ( by mid - 621 the whole province was in their hands ) and to devastate Anatolia , while the Avars and Slavs took advantage of the situation to overrun the Balkans , bringing the Roman Empire to the brink of destruction . During these years , Heraclius strove to rebuild his army , slashing non - military expenditure , devaluing the currency and melting down Church plate , with the backing of Patriarch Sergius , to raise the necessary funds to continue the war . On April 5 622 , Heraclius left Constantinople , entrusting the city to Sergius and general Bonus as regents of his son . He assembled his forces in Asia Minor , probably in Bithynia , and , after he revived their broken morale , he launched a new counter - offensive , which took on the character of a holy war ; an acheiropoietos image of Christ was carried as a military standard . The Roman army proceeded to Armenia , inflicted a defeat on an army led by a Persian - allied Arab chief , and then won a victory over the Persians under Shahrbaraz . On 25 March 624 , Heraclius again left Constantinople , with his wife Martina and his two children ; after he celebrated Easter in Nicomedia on April 15 , he campaigned in the Caucasus , winning a series of victories in Azerbaijan and Armenia against Khosrau and his generals Shahrbaraz , Shahin and Shahraplakan . In 626 the Avars and Slavs besieged Constantinople , supported by a Persian army commanded by Shahrbaraz , but the siege ended in failure ( the victory was attributed to the icons of the Virgin which were led in procession by Sergius about the walls of the city ) , while a second Persian army under Shahin suffered another crushing defeat at the hands of Heraclius ' brother Theodore . With the Persian war effort disintegrating , Heraclius was able to bring the Gokturks of the Western Turkic Khaganate into the war against the Sassanids in the Caucasus ( see Third Perso - Turkic War ) . Late in 627 he launched a winter offensive into Mesopotamia , where , despite the desertion of his Turkish allies , he defeated the Persians under Rhahzadh at the Battle of Nineveh . Continuing south along the Tigris , he sacked Khosrau ' s great palace at Dastagird and was only prevented from attacking Ctesiphon by the destruction of the bridges on the Nahrawan Canal . Discredited by this series of disasters , Khosrau was overthrown and killed in a coup led by his son Kavadh II , who at once sued for peace , agreeing to withdraw from all occupied territories . In 629 Heraclius restored the True Cross to Jerusalem in a majestic ceremony . Aftermath . The devastating impact of this last war , added to the cumulative effects of a century of almost continuous conflict , left both empires crippled . When Kavadh II died only months after coming to the throne , Persia was plunged into several years of dynastic turmoil and civil war . The Sassanids were further weakened by economic decline , heavy taxation from Khosrau II ' s campaigns , religious unrest , rigid social stratification , and the increasing power of the provincial landholders . The Roman Empire was even more severely affected , with its financial reserves exhausted by the war , the Balkans now largely in the hands of the Slavs , Anatolia devastated by repeated Persian invasions , and the empire ' s hold on Syria , Mesopotamia , Palestine and Egypt loosened by many years of Persian occupation . Neither empire was given any chance to recover , as within a few years they were struck by the onslaught of the Arabs , newly united by Islam . The Sassanid Empire rapidly succumbed to these attacks and was completely destroyed . During the Byzantine - Arab Wars , the exhausted Roman Empire ' s recently regained southern provinces were also lost during the Muslim conquest of Syria , Egypt and North Africa , reducing the empire to a territorial rump consisting of Anatolia and a scatter of islands and footholds in the Balkans and Italy . These remaining lands were thoroughly impoverished by frequent attacks , marking the transition from classical urban civilization to a more rural , medieval form of society . However , unlike Persia the Roman Empire ( in its medieval form usually termed the Byzantine Empire ) ultimately survived the Arab assault , holding onto its residual territories and repulsing two Arab sieges of its capital Constantinople in 674 and 718 .