Byzantine–Sasanian War of 602–628

Campaign map from 611 to 624 through Syria, Anatolia, Armenia, and Mesopotamia

Resistance to the Persians in Syria was not strong; although the locals constructed fortifications, they generally tried to negotiate with the Persians.[1] The cities of Damascus, Apamea, and Emesa fell quickly in 613, giving the Sasanian army a chance to strike further south into Palaestina Prima. Nicetas continued to resist the Persians but was defeated at Adhri'at. He managed to win a small victory near Emesa, however, where both sides suffered heavy casualties—the total death count was 20,000.[59] More seriously, the weakness of the resistance enabled the Persians and their Jewish allies to capture Jerusalem following a three weeks siege in 614.[60] Ancient sources claim 57,000 or 66,500 people were slain there; another 35,000 were deported to Persia, including the Patriarch Zacharias.[59]

Many churches in the city (including the Church of the Resurrection or Holy Sepulchre) were burned, and numerous relics, including the True Cross, the Holy Lance, and the Holy Sponge, were carried off to the Persian capital Ctesiphon. The loss of these relics was thought by many Christian Byzantines to be a clear mark of divine displeasure.[40] Some blamed the Jews for this misfortune and for the loss of Syria in general.[61] There were reports that Jews helped the Persians capture certain cities and that the Jews tried to slaughter Christians in cities that the Persians had already conquered but were found and foiled from doing so. These reports are likely to be greatly exaggerated and the result of general hysteria.[1]

In 618 Shahrbaraz's forces invaded Egypt, a province that had been mostly untouched by war for three centuries.[62] The Monophysites living in Egypt were unhappy with Chalcedonian orthodoxy and were not eager to aid Byzantine imperial forces. Afterward they were supported by Khosrow,[62][63] but they did not resist imperial forces between 600 and 638, and many saw the Persian occupation in negative terms.[64][65] Byzantine resistance in Alexandria was led by Nicetas. After a year-long siege, resistance in Alexandria collapsed, supposedly after a traitor told the Persians of an unused canal, allowing them to storm the city. Nicetas fled to Cyprus along with Patriarch John the Almsgiver, who was a major supporter of Nicetas in Egypt.[66] The fate of Nicetas is unclear, since he disappears from records after this, but Heraclius was presumably deprived of a trusted commander.[67] The loss of Egypt was a severe blow to the Byzantine empire, as Constantinople relied on grain shipments from fertile Egypt to feed the multitudes in the capital. The free grain ration in Constantinople, which echoed the earlier grain dole in Rome, was abolished in 618.[68]

After conquering Egypt, Khosrow allegedly sent Heraclius the following letter:[69][70]

Khosrow, greatest of Gods, and master of the earth, to Heraclius, his vile and insensate slave. Why do you still refuse to submit to our rule, and call yourself a king? Have I not destroyed the Greeks? You say that you trust in your God. Why has he not delivered out of my hand Caesarea, Jerusalem, and Alexandria? And shall I not also destroy Constantinople? But I will pardon your faults if you submit to me, and come hither with your wife and children; and I will give you lands, vineyards, and olive groves, and look upon you with a kindly aspect. Do not deceive yourself with vain hope in that Christ, who was not able to save himself from the Jews, who killed him by nailing him to a cross. Even if you take refuge in the depths of the sea, I will stretch out my hand and take you, whether you will or no.

However, the genuineness of the letter has been denied by modern scholars.[71]

When the Sasanians reached Chalcedon in 615, it was at this point, according to Sebeos, that Heraclius had agreed to stand down and was about ready to allow the Byzantine Empire to become a Persian client state, even permitting Khosrow II to choose the emperor.[72][73] Things began to look even more grim for the Byzantines when Chalcedon fell in 617 to Shahin, bringing the Persians within sight of Constantinople.[74] Shahin courteously received a peace delegation but claimed that he did not have the authority to engage in peace talks, directing Heraclius to Khosrow, who rejected the peace offer - in retrospect, a major strategic blunder.[75][76] Still, the Persian forces soon withdrew, probably to focus on their invasion of Egypt.[77][78] Yet the Persians retained their advantage, capturing Ancyra, an important military base in central Anatolia, in 620 or 622. Rhodes and several other islands in the eastern Aegean fell in 622/3, threatening a naval assault on Constantinople.[79][80][81][82] Such was the despair in Constantinople that Heraclius considered moving the government to Carthage in Africa.[68]

Solidus of Emperor Heraclius (aged 35-38). Constantinople mint. Struck 610-613. Helmeted and cuirassed facing bust, holding cross.

Khosrow's letter did not cow Heraclius but prompted him to try a desperate strike against the Persians.[74] He now reorganized the remainder of his empire to allow his forces to fight on. Already, in 615, a new, lighter (6.82 grams) silver imperial coin appeared with the usual image of Heraclius and his son Heraclius Constantine, but uniquely carried the inscription of Deus adiuta Romanis or "May God help the Romans"; Kaegi believes this shows the desperation of the empire at this time.[83] The copper follis also dropped in weight from 11 grams to somewhere between 8 and 9 grams. Heraclius faced severely decreased revenues due to the loss of provinces; furthermore, a plague broke out in 619, which further damaged the tax base and also increased fears of divine retribution.[84] The debasement of the coinage allowed the Byzantines to maintain expenditure in the face of declining revenues.[83]

Heraclius now halved the pay of officials, enforced increased taxation, forced loans, and levied extreme fines on corrupt officials in order to finance his counter-offensive.[85] Despite disagreements over the incestuous marriage of Heraclius to his niece Martina, the clergy of the Byzantine Empire strongly backed his efforts against the Persians by proclaiming the duty of all Christian men to fight and by offering to give him a war loan consisting of all the gold and silver-plated objects in Constantinople. Precious metals and bronze were stripped from monuments and even the Hagia Sophia.[86] This military campaign has been seen as the first "crusade", or at least as an antecedent to the Crusades, by many historians, beginning with William of Tyre,[70][74][87][88] but some, like Kaegi, disagree with this moniker because religion was just one component in the war.[89] Thousands of volunteers were gathered and equipped with money from the church.[74] Heraclius himself decided to command the army from the front lines. Thus, the Byzantine troops had been replenished, re-equipped, and were now led by a competent general—while maintaining a full treasury.[74]

Historian George Ostrogorsky believed that volunteers were gathered through the reorganization of Anatolia into four themes, where the volunteers were given inalienable grants of land on the condition of hereditary military service.[90] However, modern scholars generally discredit this theory, placing the creation of the themes later, under Heraclius' successor Constans II.[91][92]

By 622, Heraclius was ready to mount a counter-offensive. He left Constantinople the day after celebrating Easter on Sunday, 4 April 622.[93] His young son, Heraclius Constantine, was left behind as regent under the charge of Patriarch Sergius and the patrician Bonus. He spent the summer training to improve the skills of his men and his own generalship. In the autumn, Heraclius threatened Persian communications from the Euphrates valley to Anatolia by marching to Cappadocia.[85] This forced the Persian forces in Anatolia under Shahrbaraz to retreat from the front-lines of Bithynia and Galatia to eastern Anatolia in order to block his access to Iran.[94]

What followed next is not entirely clear, but Heraclius certainly won a crushing victory over Shahrbaraz in the fall of 622.[95] The key factor was Heraclius' discovery of Persian forces hidden in ambush and responding by feigning retreat during the battle. The Persians left their cover to chase the Byzantines, whereupon Heraclius' elite Optimatoi assaulted the pursuing Persians, causing them to flee.[94] Thus he saved Anatolia from the Persians. Heraclius had to return to Constantinople, however, to deal with the threat posed to his Balkan domains by the Avars, so he left his army to winter in Pontus.[85][96]

While the Byzantines were occupied with the Persians, the Avars and Slavs poured into the Balkans, capturing several Byzantine cities, including Singidunum (Belgrade), Viminacium (Kostolac), Naissus (Niš), and Serdica (Sofia), while destroying Salona in 614. Isidore of Seville even claims that the Slavs took "Greece" from the Byzantines.[97] The Avars also began to raid Thrace, threatening commerce and agriculture, even near the gates of Constantinople.[97] However, numerous attempts by the Avars and Slavs to take Thessalonica, the most important Byzantine city in the Balkans after Constantinople, ended in failure, allowing the Empire to hold onto a vital stronghold in the region.[98] Other minor cities on the Adriatic coast like Jadar (Zadar), Tragurium (Trogir), Butua (Budva), Scodra (Shkodër), and Lissus (Lezhë) also survived the invasions.[99]

Because of the need to defend against these incursions, the Byzantines could not afford to use all their forces against the Persians. Heraclius sent an envoy to the Avar Khagan, saying that the Byzantines would pay a tribute in return for the Avars withdrawing north of the Danube.[74] The Khagan replied by asking for a meeting on 5 June 623, at Heraclea in Thrace, where the Avar army was located; Heraclius agreed to this meeting, coming with his royal court.[100] The Khagan, however, put horsemen en route to Heraclea to ambush and capture Heraclius, so they could hold him for ransom.[101]

Heraclius was fortunately warned in time and managed to escape, chased by the Avars all the way to Constantinople. However, many members of his court, as well as an alleged 70,000 Thracian peasants who came to see their Emperor, were captured and killed by the Khagan's men.[102] Despite this treachery, Heraclius was forced to give the Avars a subsidy of 200,000 solidi along with his illegitimate son John Athalarichos, his nephew Stephen, and the illegitimate son of the patrician Bonus as hostages in return for peace. This left him more able to focus his war effort completely on the Persians.[101][103]

Heraclius offered peace to Khosrow, presumably in 624, threatening otherwise to invade Iran, but Khosrow rejected the offer.[104] On March 25, 624, Heraclius left Constantinople to attack the Persian heartland. He willingly abandoned any attempt to secure his rear or his communications with the sea,[104] marching through Armenia and modern Azerbaijan to assault the core Persian lands directly.[85] According to Walter Kaegi, Heraclius led an army of no more than 40,000, and most likely between 20,000–24,000.[105] Before journeying to the Caucasus, he recovered Caesarea in Cappadocia, in defiance of the earlier letter that Khosrow had sent him.[105]

Adur Gushnasp, a major Persian fire temple belonging to the Warrior class, destroyed during the Roman campaign. Major Christian holy sites were destroyed after the Persian-Jewish capture of Jerusalem earlier in the war.

Heraclius advanced along the Araxes River, destroying Persian-held Dvin, the capital of Armenia, and Nakhchivan. At Ganzaka, Heraclius met Khosrow's army, some 40,000 strong. With the help of loyal Arabs, he captured and killed some of Khosrow's guards, leading to the disintegration of the Persian army. Heraclius then destroyed Adur Gushnasp, the famous Zoroastrian fire temple at Takht-i-Suleiman.^[e][106] Heraclius' raids went as far as the Gayshawan, a residence of Khosrow in Adurbadagan.[106]

Campaign map of Heraclius in 624, 625, and 627–628 through Armenia, Anatolia, and Mesopotamia

Heraclius wintered in Caucasian Albania, gathering forces for the next year.[107] Khosrow was not content to let Heraclius quietly rest in Albania. He sent three armies, commanded by Shahrbaraz, Shahin, and Shahraplakan, to try to trap and destroy Heraclius' forces.[108] Shahraplakan retook lands up as far as Siwnik, aiming to capture the mountain passes. Shahrbaraz was sent to block Heraclius' retreat through Caucasian Iberia, and Shahin was sent to block the Bitlis Pass. Heraclius, planning to engage the Persian armies separately, spoke to his worried Lazic, Abasgian, and Iberian allies and soldiers, saying: "Do not let the number of our enemies disturb us. For, God willing, one will pursue ten thousand."[108]

Two soldiers who feigned desertion were sent to Shahrbaraz, claiming that the Byzantines were fleeing before Shahin. Due to jealousy between the Persian commanders, Shahrbaraz hurried with his army to take part in the glory of the victory. Heraclius met them at Tigranakert and routed the forces of Shahraplakan and Shahin one after the other. Shahin lost his baggage train, and Shahraplakan (according to one source) was killed, though he re-appears later.[108][109][110] After this victory, Heraclius crossed the Araxes and camped in the plains on the other side. Shahin, with the remnants of both his and Shahraplakan's armies, joined Shahrbaraz in the pursuit of Heraclius, but marshes slowed them down.[109][110] At Aliovit, Shahrbaraz split his forces, sending some 6,000 troops to ambush Heraclius while the remainder of the troops stayed at Aliovit. Heraclius instead launched a surprise night attack on the Persian main camp in February 625, destroying it. Shahrbaraz only barely escaped, naked and alone, having lost his harem, baggage, and men.[109]

Heraclius spent the rest of winter to the north of Lake Van.[109] In 625, his forces attempted to push back towards the Euphrates. In a mere seven days, he bypassed Mount Ararat and the 200 miles along the Arsanias River to capture Amida and Martyropolis, important fortresses on the upper Tigris.[85][111][112] Heraclius then carried on towards the Euphrates, pursued by Shahrbaraz. According to Arab sources, he was stopped at the Satidama or Batman Su River and defeated; Byzantine sources, however, do not mention this incident.[112] There was then another minor skirmish between Heraclius and Shahrbaraz at the Sarus River near Adana.[113] Shahrbaraz stationed his forces across the river from the Byzantines.[85] A bridge spanned the river, and the Byzantines immediately charged across. Shahrbaraz feigned retreat to lead the Byzantines into an ambush, and the vanguard of Heraclius' army was destroyed within minutes. The Persians, however, had neglected to cover the bridge, and Heraclius charged across with the rearguard, unafraid of the arrows that the Persians fired, turning the tide of battle against the Persians.[114] Shahrbaraz expressed his admiration at Heraclius to a renegade Greek: "See your Emperor! He fears these arrows and spears no more than would an anvil!"[114] The Battle of Sarus was a successful retreat for the Byzantines that panegyrists magnified.[113] In the aftermath of the battle, the Byzantine army wintered at Trebizond.[114]

Siege of Constantinople in 626 by the combined Sasanian, Avar, and Slavic forces depicted on the murals of the Moldovița Monastery, Romania

Khosrow, seeing that a decisive counterattack was needed to defeat the Byzantines, recruited two new armies from all the able men, including foreigners.[114] Shahin was entrusted with 50,000 men and stayed in Mesopotamia and Armenia to prevent Heraclius from invading Iran; a smaller army under Shahrbaraz slipped through Heraclius' flanks and bee-lined for Chalcedon, the Persian base across the Bosphorus from Constantinople. Khosrow also coordinated with the Khagan of the Avars so as to launch a coordinated attack on Constantinople from both European and Asiatic sides.[111] The Persian army stationed themselves at Chalcedon, while the Avars placed themselves on the European side of Constantinople and destroyed the Aqueduct of Valens.[115] Because of the Byzantine navy's control of the Bosphorus strait, however, the Persians could not send troops to the European side to aid their ally.[116][117] This reduced the effectiveness of the siege, because the Persians were experts in siege warfare.[118] Furthermore, the Persians and Avars had difficulties communicating across the guarded Bosphorus—though undoubtedly, there was some communication between the two forces.[111][117][119]

The defense of Constantinople was under the command of Patriarch Sergius and the patrician Bonus.[120] Upon hearing the news, Heraclius split his army into three parts; although he judged that the capital was relatively safe, he still sent some reinforcements to Constantinople to boost the morale of the defenders.[120] Another part of the army was under the command of his brother Theodore and was sent to deal with Shahin, while the third and smallest part would remain under his own control, intending to raid the Persian heartland.[114]

Cherub and Heraclius receiving the submission of Khosrow II; plaque from a cross (Champlevé enamel over gilt copper, 1160-1170, Louvre, Paris). This is only an allegory, since Khosrow never submitted in person to Heraclius.

On 29 June 626, a coordinated assault on the walls began. Inside the walls, some 12,000 well-trained Byzantine cavalry troops (presumably dismounted) defended the city against the forces of some 80,000 Avars and Slavs.[114] Despite continuous bombardment for a month, morale was high inside the walls of Constantinople because of Patriarch Sergius' religious fervor and his processions along the wall with the icon of the Virgin Mary, inspiring the belief that the Byzantines were under divine protection.[121][122]

On 7 August, a fleet of Persian rafts ferrying troops across the Bosphorus were surrounded and destroyed by Byzantine ships. The Slavs under the Avars attempted to attack the sea walls from across the Golden Horn, while the main Avar host attacked the land walls. Patrician Bonus' galleys rammed and destroyed the Slavic boats; the Avar land assault from August 6 to the 7th also failed.[123] With the news that Theodore had decisively triumphed over Shahin (supposedly leading Shahin to die from depression), the Avars retreated to the Balkan hinterland within two days, never to seriously threaten Constantinople again. Even though the army of Shahrbaraz was still encamped at Chalcedon, the threat to Constantinople was over.[120][121] In thanks for the lifting of the siege and the supposed divine protection of the Virgin Mary, the celebrated Akathist Hymn was written by an unknown author, possibly Patriarch Sergius or George of Pisidia.[124][125][126]

Furthermore, after the emperor showed Shahrbaraz intercepted letters from Khosrow ordering the Persian general's death, the latter switched to Heraclius' side.[127] Shahrbaraz then moved his army to northern Syria, where he could easily decide to support either Khosrow or Heraclius at a moment's notice. Still, with the neutralization of Khosrow's most skilled general, Heraclius deprived his enemy of some of his best and most experienced troops, while securing his flanks prior to his invasion of Iran.[128]

Western Turk officers during a audience with king Varkhuman of Samarkand. 648-651 CE, Afrasiyab murals, Samarkand.[129][130][131]

During the siege of Constantinople, Heraclius formed an alliance with people Byzantine sources called the "Khazars", under Ziebel, now generally identified as the Western Turkic Khaganate of the Göktürks, led by Tong Yabghu,[132] plying him with wondrous gifts and the promise of marriage to the porphyrogenita Eudoxia Epiphania. Earlier, in 568, the Turks under Istämi had turned to Byzantium when their relations with Iran soured over commerce issues.[133] Istämi sent an embassy led by the Sogdian diplomat Maniah directly to Constantinople, which arrived in 568 and offered not only silk as a gift to Justin II, but also proposed an alliance against Sasanian Iran. Justin II agreed and sent an embassy to the Turkic Khaganate, ensuring the direct Chinese silk trade desired by the Sogdians.[134][135]

In the East, in 625, the Turks took advantage of the Sasanian weakness to occupy Bactria and Afghanistan as far as the Indus, and establish the Yabghus of Tokharistan.[136]

The Turks, based in the Caucasus, responded to the alliance by sending 40,000 of their men to ravage the Iranian Empire in 626, marking the start of the Third Perso-Turkic War.[114] Joint Byzantine and Göktürk operations were then focused on besieging Tbilisi , where the Byzantines used traction trebuchets to breach the walls, one of the first known uses by the Byzantines.^[f][137] Khosrow sent 1,000 cavalry under Shahraplakan to reinforce the city,[138] but it nevertheless fell, probably in late 628.[139] Ziebel died by the end of that year, however, saving Epiphania from marriage to a barbarian.[114] Whilst the siege proceeded, Heraclius worked to secure his base in the upper Tigris.[120]

Maneuvers before and after the Battle of Nineveh

In mid-September 627, Heraclius invaded the Iranian heartland in a surprising winter campaign, leaving Ziebel to continue the siege of Tiflis. Edward Luttwak describes the seasonal retreat of Heraclius for the winters of 624–626 followed by a change in 627 to threaten Ctesiphon as a "high-risk, relational maneuver on a theater-wide scale" because it habituated the Persians to strategically ineffective raids that caused them to decide not to recall border troops to defend the heartland.[140] His army numbered between 25,000 and 50,000 Byzantine troops and 40,000 Göktürks that quickly deserted him because of the unfamiliar winter conditions and harassment from the Persians.[141][142] He advanced quickly but was tailed by a Persian army under the Armenian Rhahzadh, who faced difficulties in provisioning his army due to the Byzantines taking most of the provisions as they moved south toward Assyria.[142][143][144]

Towards the end of the year, near the ruins of Nineveh, Heraclius engaged Rhahzadh before reinforcements could reach the Persian commander.[145] The Battle of Nineveh took place in the fog, reducing the Persian advantage in missile troops. Heraclius feigned retreat, leading the Persians to the plains, before reversing his troops to the surprise of the Persians.[146] After eight hours of fighting, the Persians suddenly retreated to nearby foothills, but the battle did not become a rout.[121][147] During the battle, approximately 6,000 Persians were killed.[148] Patriarch Nikephoros' Brief History suggests that Rhahzadh challenged Heraclius to personal combat, and that Heraclius accepted and killed Rhahzadh in a single thrust; two other challengers fought against him and also lost.[121][149] However, he received an injury to his lip.[150]

Heraclius in 629-632 (aged 54-57), with his son.

With no Persian army left to oppose him, Heraclius' victorious army plundered Dastagird, which was a palace of Khosrow's, and gained tremendous riches while recovering 300 captured Byzantine flags.[151] Khosrow had already fled to the mountains of Susiana to try to rally support for the defense of Ctesiphon.[120][121] Heraclius then issued an ultimatum to Khosrow:

I pursue and run after peace. I do not willingly burn Persia, but compelled by you. Let us now throw down our arms and embrace peace. Let us quench the fire before it burns up everything.

— Heraclius' ultimatum to Khosrow II, 6 January 628[152]

However, Heraclius could not attack Ctesiphon itself, as the Nahrawan Canal was blocked due to the collapse of a bridge leading over it,[151] and he did not attempt to bypass the canal.[153]

Regardless, the Persian army rebelled and overthrew Khosrow II, raising his son Kavadh II, also known as Siroes, in his stead. Khosrow was shut in a dungeon, where he suffered for five days on bare sustenance—he was shot to death slowly with arrows on the fifth day.[154] Kavadh immediately sent peace offers to Heraclius. Heraclius did not impose harsh terms, knowing that his own empire was also near exhaustion. Under the terms of the peace treaty, the Byzantines regained all their lost territories, their captured soldiers, a war indemnity, and most importantly for them, the True Cross and other relics that were lost in Jerusalem in 614.[154][155][156]

Heraclius returns the True Cross to Jerusalem, anachronistically accompanied by Saint Helena. 15th century, Spain

After some months of travel, Heraclius entered Constantinople in triumph and was met by the people of the city, his son Heraclius Constantine, and Patriarch Sergius, prostrating themselves in joy.[157] His alliance with the Persians resulted in the recovery of the Holy Sponge which fastened to the True Cross in an elaborate ceremony on 14 September 629.[158] The ceremonial parade went toward the Hagia Sophia. There, the True Cross was slowly raised up until it vertically towered over the high altar. To many, this was a sign that a new golden age was about to begin for the Byzantine Empire.[154][159]

The conclusion of the war cemented Heraclius' position as one of history's most successful generals. He was hailed as "the new Scipio" for his six years of unbroken victories and for leading the Roman army where no Roman army had ever gone before.[70][155] The triumphal raising of the True Cross in the Hagia Sophia was a crowning moment in his achievements. Had Heraclius died then, he would have been recorded in history, in the words of the historian Norman Davies, as "the greatest Roman general since Julius Caesar".[70] Instead, he lived through the Arab invasions, losing battle after battle against their onslaught and tarnishing his reputation for victory. Lord Norwich succinctly described Heraclius as having "lived too long".[160]

For their part, the Sasanians struggled to establish a stable government. When Kavadh II died only months after coming to the throne, Persia was plunged into several years of dynastic turmoil and civil war. Ardashir III, Heraclius' ally Shahrbaraz, and Khosrow's daughters Purandokht and Azarmidokht all succeeded to the throne within months of each other. Only when Yazdgerd III, a grandson of Khosrow II, succeeded to the throne in 632 was there stability, but by then it was too late to rescue the Sasanian kingdom.[161][162]

The devastating impact of the war of 602–628, along with the cumulative effects of a century of almost continuous Byzantine-Persian conflict, left both empires crippled. The Sasanians were further weakened by economic decline, heavy taxation to finance Khosrow II's campaigns, religious unrest, and the increasing power of the provincial landholders at the expense of the Shah.[163] According to Howard-Johnston: "[Heraclius'] victories in the field over the following years and their political repercussions ... saved the main bastion of Christianity in the Near East and gravely weakened its old Zoroastrian rival. They may be shadowed by the even more extraordinary military achievements of the Arabs in the following two decades, but hindsight should not be allowed to dim their lustre."[164]

However, the Byzantine Empire was also severely affected, with the Balkans now largely in the hands of the Slavs.[165] Additionally, Anatolia had been devastated by repeated Persian invasions, and the empire's hold on its recently regained territories in the Caucasus, Syria, Mesopotamia, Palestine, and Egypt was loosened by years of Persian occupation.^[g][166] With their financial reserves exhausted, the Byzantines found difficulties paying veterans of the war with the Persians and recruiting new troops.[165][167][168] Clive Foss called this war the "first stage in the process which marked the end of Antiquity in Asia Minor".[169]

Neither empire was given much chance to recover, as within a few years they were struck by the onslaught of the Arabs, newly united by Islam,[170] which Howard-Johnston likened to "a human tsunami".[171] According to George Liska, the "unnecessarily prolonged Byzantine–Persian conflict opened the way for Islam".[172] The Sasanian Empire rapidly succumbed to these attacks and was completely destroyed. During the Byzantine–Arab Wars, the exhausted Byzantine Empire's recently regained eastern and southern provinces of Syria, Armenia, Egypt, and North Africa were also lost, reducing the empire to a territorial core consisting of Anatolia and a scatter of islands and footholds in the Balkans and Italy.[166] However, unlike Persia, the Byzantine Empire ultimately survived the Arab assault, holding onto its remaining territories and decisively repulsing two Arab sieges of its capital in 674–678 and 717–718.[164][173] The Byzantine Empire also lost its territories in Crete and southern Italy to the Arabs in later conflicts, though these too were ultimately recovered.[174][175] However, some losses were permanent, such as the loss of Spania, the remaining Byzantine holdings in the Iberian Peninsula, which was conquered by the Visigoths by 629.[176] Similarly, Corsica was taken by the Lombards in the 8th century.[177] The Balearic Islands, Sardinia and Sicily were captured by Arabs in the 10th century.[178]

^ a: All dates, especially between 602–620 are only approximate. This is primarily because many popular sources like Theophanes' Chronicles are all drawn from a common source, thought to be a history by Theophilus of Edessa. Thus, there are few independent witnesses of the following events, making reliable dating difficult.[197]
^ b: The war had originally begun when Justin II had refused to give the Sasanians the usual tribute dating from the time of Justinian I. The successful conclusion to that war meant that the tribute was no longer paid.[209]
^ c: Some authors, including Dodgeon, Greatrex, and Lieu, have expressed the belief that the raid on Chalcedon is fictitious.[48] Either way, by 610, the Persians captured all the Byzantine cities east of the Euphrates.[47]
^ e: Thebarmes, described in Theophanes' Chronicles, is usually identified with Takht-i-Suleiman.[210]
^ f: That was the first known usage of the term helepolis to describe the trebuchet, though earlier uses may be attested to in Emperor Maurice's Strategikon.[211]
^ g: Ambivalence toward Byzantine rule on the part of monophysites may have lessened local resistance to the Arab expansion.[166]