The Battle of al-Qadisiyyah (Arabic: مَعْرَكَة ٱلْقَادِسِيَّة, romanized: Maʿrakat al-Qādisīya; Persian: نبرد قادسیه, romanized: Nabard-i Qādisiya) took place between the armies of the Rashidun Caliphate and the Sasanian Empire in November 636. It resulted in a decisive victory for the Rashidun army and is considered to be one of the most significant engagements of the Muslim conquest of Persia, and thereby of the early Muslim conquests as a whole. After losing al-Qadisiyyah, the Sasanian army was left unable to defend against the Rashidun siege of Ctesiphon, thus being forced to retreat from all of Mesopotamia. This development enabled further Rashidun offensives into the Persian mainland and culminated in the Sasanian Empire's annexation by 651.
It is widely believed that the Rashidun army's advance on al-Qadisiyyah began on 16 November 636 and continued for the next three days. During the battle, Sasanian troops were thrown into disarray following the death of their general Rustam Farrokhzad under uncertain circumstances. The ensuing collapse of their positions marked a cataclysmic defeat that led to the Rashidun army's seizure of Ctesiphon, which had served as the Persian capital city since the Parthian period.
The Rashidun Caliphate's success in capturing al-Qadisiyyah was key to conquering the Sasanian province of Asoristan, and was followed by major engagements at Jalula and Nahavand. The battle allegedly saw the establishment of an alliance between the Sasanian Empire and the Byzantine Empire. This purported alliance, for the Byzantines, was motivated by the contemporary Rashidun invasion of the Levant and Egypt.
In 2024, scholars and researchers from Durham University and the University of al-Qadisiyyah identified the likely site of the battle to an open field situated approximately 19 kilometres (12 mi) to the south of modern-day Kufa.
Background
Byzantine–Sasanian War of 602–628
After the assassination of Byzantine emperor Maurice by pretender Emperor Phocas, the shah of the Sasanian Empire, Khosrow II, declared war on the Byzantine Empire, starting the Byzantine–Sasanian War of 602–628. Forces of the Sasanian Empire invaded and captured Syria, Egypt, and Anatolia, and carried the True Cross away in triumph.
After being deposed in 610, Phocas was succeeded by Heraclius, who led the Byzantines in a war of reconquest, successfully regaining territory lost to the Sasanians. Heraclius defeated a small Persian army at the final Battle of Nineveh and advanced towards Ctesiphon.
During this period, Khosrow II was overthrown and executed by one of his sons, Kavadh II. Kavadh subsequently made peace with the Byzantines and returned all captured territories as well as the True Cross. The Göktürks, who were attacking the north of Persia with a massive army during the peace proceedings, were ordered by Heraclius to retreat after the signing of the pact with Kavadh.
Sasanian Civil War of 628–632
After a few short months of reign, Kavadh II suddenly died of the plague; the ensuing power vacuum quickly led to a civil war. Ardashir III (c. 621–630), son of Kavadh II, was raised to the throne at age seven, but was killed 18 months later by his general, Shahrbaraz, who then declared himself ruler. In 613 and 614, Shahrbaraz took both Damascus and Jerusalem from the Byzantine Empire, respectively.
On 9 June 629, Shahrbaraz was killed during an invasion from Armenia by a Khazar–Göktürk force under Chorpan Tarkhan. He was succeeded by Boran, a daughter of Khosrow II. She was the 26th sovereign monarch of Persia, ruling from 17 June 629 to 16 June 630, and was one of only two women to sit on the Sasanian throne, the other being her sister Azarmidokht (r. 630–631). She was made empress regnant on the understanding that she would vacate the throne upon Yazdegerd III (632–651), the son of Shahriyar and grandson of Khosrow II, attaining majority.
Boran attempted to bring stability to the empire by implementing justice, reconstructing and fixing infrastructure, lowering taxes, minting coins, and signing a peace treaty with the Byzantine Empire. She also appointed Rustam Farrokhzād as the commander-in-chief of the Persian army.
However, Boran was largely unsuccessful in restoring power to the central authority, which had been weakened considerably by civil wars, and either resigned or was murdered soon after ascending to the throne. She was replaced by her sister Azarmidokht, who in turn was replaced by Hormizd VI, a noble of the Persian court.
After five years of internal power struggle, Yazdegerd III, grandson of Khosrow II, became emperor at the age of eight in 632. The real power of the Persian state was held in the hands of generals Rustam Farrokhzād and Piruz Khosrow (also known as Piruzan).
The coronation of Yazdegerd III infused new life into the Sasanian Empire.
First Muslim campaign
Muhammad's death and Rashidun wars
After the death of Muhammad, Abu Bakr established control over Arabia through the Ridda Wars and then launched campaigns against the remaining territories of Syria and Palestine. He triggered the chain of events that would in a few decades form one of the largest empires the world had ever seen. This put the nascent Islamic empire on a collision course with the Byzantine and Sasanian empires, which were the two superpowers of the time. The wars soon became a matter of conquest that would eventually result in the demise of the Sasanian Empire and the annexation of all of the Byzantine Empire's southern and eastern territories. To make victory certain, Abu Bakr decided that the invading army would consist entirely of volunteers and would be commanded by his best general, Khalid ibn al-Walid. Khalid won quick victories in four consecutive battles: the Battle of Chains, fought in April 633; the Battle of River, fought in the third week of April 633; the Battle of Walaja, fought in May 633; followed by the decisive Battle of Ullais, fought in mid-May, 633. By now the Persian Empire was struggling, and in the last week of May 633, the capital city of Iraq, Al-Hirah, fell to the Muslims after the Battle of Hira. Thereafter, the Siege of Al-Anbar during June–July 633 resulted in the surrender of the city after strong resistance. Khalid then moved towards the south and conquered the city of Ein ul Tamr after the Battle of Ayn al-Tamr in the final week of July 633. In November 633, the Persian counterattack was repulsed by Khalid. In December 633, Muslim forces reached the border city of Firaz, where Khalid defeated the combined Sasanian, Byzantine, and Christian Arab armies in the Battle of Firaz. This was the last battle in the conquest of Iraq.
Byzantine counteroffensive in the Levant
By this time, except for Ctesiphon, Khalid had captured all of Iraq. However, circumstances changed on the western front. The Byzantine army soon came into direct conflict in Syria and Palestine, and Khalid was sent with half of his army to deal with this new development. Soon after, Caliph Abu Bakr died in August 634 and was succeeded by Caliph Umar ibn al-Khattāb. Muslim forces in Iraq were too few in number to control the region. After the devastating invasion by Khalid, the Persians took time to recover; political instability was at its peak at Ctesiphon. Once the Persians recovered, they concentrated more troops and mounted a counterattack. Al-Muthanna ibn Haritha, who was now commander-in-chief of the Muslim forces in Iraq, pulled his troops back from all outposts and evacuated Al-Hirah. He then retreated to the region near the Arabian Desert. Meanwhile, Umar sent reinforcements from Madinah under the command of Abu Ubaid. The reinforcements reached Iraq in October 634, and Abu Ubaid assumed the command of the army and defeated the Sasanians at the Battle of Namaraq near modern-day Kufa. Then, in the Battle of Kaskar, he recaptured Hira.
Sasanian counteroffensive in Mesopotamia
The Persians launched another counterattack and defeated the Muslims at the Battle of the Bridge, which killed Abu Ubaid, and the Muslims suffered heavy losses. Muthanna then assumed command of the army and withdrew the remnant of his forces, about 3000 strong, across the Euphrates. The Persian commander Bahman (also known as Dhu al-Hajib) was committed to driving the Muslims away from Persian soil but was restrained from pursuing the defeated Muslims after being called back by Rustum to Ctesiphon, to help in putting down the revolt against him. Muthanna retreated near the frontier of Arabia and called for reinforcements. After getting sufficient reinforcements, he re-entered the fray and camped at the western bank of the Euphrates, where a Persian force intercepted him and was defeated.
After Khalid left Iraq for Syria, Suwad, the fertile area between the Euphrates and the Tigris, remained unstable. Sometimes it was occupied by the Persians and sometimes by the Muslims. This "tit-for-tat" struggle continued until emperor Yazdegerd III consolidated his power and sought an alliance with Heraclius in 635 in an effort to prepare for a massive counterattack. Heraclius then prepared for a major offensive in the Levant. Meanwhile, Yazdegerd ordered a concentration of massive armies to reclaim Iraq for good. This was supposed to be a well-coordinated attack by both emperors to annihilate the power of their common enemy, Caliph Umar.
When Heraclius launched his offensive in May 636, Yazdegerd could not coordinate on time, so the plan was not carried out as planned. Meanwhile, Umar allegedly had knowledge of this alliance and devised his own plan to counteract it. He wanted to finish the Byzantines first, and later deal with the Persians separately. Accordingly, he sent 6,000 soldiers as reinforcements to his army in Yarmouk who were facing off the Byzantine army. Simultaneously, Umar engaged Yazdegerd III, ordering Sa'd ibn Abi Waqqas to enter into peace negotiations with him by inviting him to convert to Islam. Heraclius, fearing the above-mentioned scenario had instructed his general Vahan not to engage in battle with Muslims and await his orders. However, Vahan, witnessing fresh reinforcements for the Muslims arriving daily from Madinah, felt compelled to attack the Muslim forces before they got too strong. Heraclius's imperial army was annihilated at Battle of Yarmouk in August 636, three months before the battle of Qadisiyyah, therefore ending the Roman Emperor's offensive in the west. Undeterred, Yazdegerd continued to execute his plan of attack and concentrated armies near his capital Ctesiphon. A large force was put under the control of veteran general Rustam and was cantoned at Valashabad near Ctesiphon. Receiving news of preparations for a massive counterattack, Umar ordered Muthana to abandon Iraq and retreat to the edge of the Arabian Desert. The Iraqi campaign would be addressed at a later date.
Second Muslim campaign
Rashidun preparations
Caliph Umar started raising new armies from throughout Arabia with the intention of re-invading Iraq. Umar appointed Sa'd ibn Abī Waqqās, an important member of the Quraysh tribe as commander of this army. In May 636, Sa'd was instructed to march to Northern Arabia with a contingent of 4,000 men from his camp at Sisra (near Madinah) and take over command of the Muslim army, and immediately march onward to Iraq. Because of his inexperience as a general, he was instructed by Caliph Umar to seek the advice of experienced commanders before making critical decisions. Umar sent orders to him to halt at al-Qadisiyyah, a small town 30 miles from Kufah.
Umar continued to remotely issue strategic orders and commands to his army throughout the campaign. Due to a shortage of manpower, Umar decided to lift the ban on the ex-apostate tribes of Arabia from participating in state affairs. The army raised was not professional but a volunteer force composed of newly recruited contingents from all over Arabia. After a decisive victory against the Byzantine army at the Yarmouk, Umar sent immediate orders to Abu Ubaidah to send a contingent of veterans to Iraq. A force of 5,000 veterans of Yarmouk was also sent to Qadisiyyah, arriving on the second day of the battle there. This proved to be a major turning point and a major morale booster for the Muslim army. The battle of Qadisiyyah was fought predominantly between Umar and Rustam, rather than between Sa'd and Rustam. Coincidentally, the bulk of the Sasanian army was also made up of new recruits, since the bulk of the regular Sasanian forces was destroyed during the Battles of Walaja and Ullais.
Qadisiyyah was a small town on the west bank of the river Ateeq, a branch of the Euphrates. Al-Hira, the ancient capital of Lakhmid Dynasty, was about thirty miles west. According to present-day geography, it is situated in the southwest of al-Hillah and Kufah in Iraq. The precise location of the battlefield has been determined by archeologists at the University of Durham in England and the University of Al-Qadisiyah in Iraq, utilizing American declassified spy satellite imagery and historical texts describing the Darb Zubaydah (DZ), a Hajj pilgrimage road.
Troop strength and deployment
Modern estimates suggest that the size of the Sasanian forces was about 30,000 strong and that of the Muslims was around 30,000 strong after being reinforced by the Syrian contingent on the second day of the battle. These figures come from studying the logistical capabilities of the combatants, the sustainability of their respective bases of operations, and the overall manpower constraints affecting the Sasanians and Muslims. Most scholars, however, agree that the Sasanian army and their allies outnumbered the Muslims by a sizable margin.