His reign saw the uprising of Vakhtang I of Iberia, as well as the Anastasian War and the Iberian War against the Sasanians' archrival, the neighboring Byzantines. During Kavadh's reign, massive fortification activities were conducted in the Caucasus, including Derbent.
Kavadh was born in 449. After the Sasanian disaster at the battle of Herat, only few members of the royal line remained; according to Procopius, of the ca. 30 sons of Peroz I. He was, however, in captivity under the Hephthalites, and was later rescued by the Karenid Sukhra, who managed to defeat their leader Khushnavaz. After this victory, Kavadh and Sukhra returned to Ctesiphon, where Balash was crowned as king of the Empire. However, in reality it was Sukhra who had control over the Sasanian Empire. Gushnaspdad, the kanarang of Abarshahr, urged the Sasanian nobles to have Kavadh executed.
However, the Sasanian nobles declined the suggestion and instead had Kavadh imprisoned. He later managed to escape and took refugee in Central Asia. In 488, Kavadh returned to Persia with the aid of the Hephthalites, and was joined by other Sasanian nobles, who included Adergoudounbades, a relative of Gushnaspdad. During the revolt of Kavadh, Sukhra told Balash that he was unsuitable to rule as the king of Sasanian Empire and had him deposed in favor of Kavadh. The new Sasanian king then had Gushnaspdad executed, and he was replaced by Adergoudounbades as kanarang.
Even after the ascension of a new Sasanian king, Sukhra still possessed a massive amount of power; according to Ferdowsi, Sukhra controlled all except the kingly crown. Al-Tabari says the following thing about Sukhra's power: "Sukhra was in charge of government of the kingdom and the management of affairs. The people came to Sukhra and undertook all their dealings with him, treating Kavadh as a person of no importance and regarding his commands with contempt."
In 493 Kavadh tried to reduce the power of Sukhra by sending him to his native city in Pars, and later, with the aid of Shapur of Ray, defeated Sukhra's loyalists, and captured the latter. Sukhra was then brought to Ctesiphon where he was executed.
Vakhtang I, the incumbent Chosroid king, was on friendly terms with the Sasanian kings prior to Kavadh I, and joined them on various expeditions and in numerous wars. However, decades later, by espousing pro-Roman policy, the latter who were the archrivals of the Sasanians, Vakhtang further alienated his nobles, who sought Iranian support against the king’s encroachments on their autonomy, as he was strengthening his royal authority. In 482, Vakhtang put to death his most influential vassal, Varsken, vitaxa of Gogarene, a convert to Zoroastrianism and a champion of Iran’s influence in the Caucasus, who had executed his Christian wife, Shushanik, daughter of the Armenian Mamikonid prince Vardan II and a hero of the earliest surviving piece of Georgian literature. By this act, Vakhtang placed himself in open confrontation with his Iranian suzerain. Vakhtang called on the Armenian princes and the Huns for co-operation. After some hesitation, the Armenians under Vardan’s nephew Vahan Mamikonian, joined forces with Vakhtang. The allies were routed and Iberia was ravaged by Iranian punitive expeditions in 483 and 484, forcing Vakhtang into flight to Roman-controlled Lazica (modern western Georgia). After Peroz’s death in the war with the Hephthalites in 484, his successor Balash reestablished peace in the Caucasus. Vakhtang was able to resume his reign in Iberia, but did not betray his pro-Roman line.
Once the Hundred Years Peace between Iran and the Eastern Roman Empire collapsed, Kavadh I summoned Vakhtang as a vassal to join in a new campaign against the Romans. Vakhtang refused, provoking an Iranian invasion of his kingdom. Then about 60, he had to spend the last years of his life in war and exile, fruitlessly appealing for the Roman aid. The chronology of this period is confused, but by 518 an Iranian viceroy had been installed at the Iberian town of Tiflis, founded - according to Georgian tradition - by Vakhtang and designated as the country’s future capital. According to the LVG, Vakhtang died fighting an Iranian invading army at the hands of his renegade slave who shot him through an armpit defect of his armor. The wounded king was transported to his castle at Ujarma where he died and was interred at the cathedral in Mtskheta. Javakhishvili puts Vakhtang’s death at c. 502. If Toumanoff’s identification of Procopius’ Gurgenes with Vakhtang is true, the king might have ended his reign in 522 by taking refuge in Lazica, where he possibly died around the same time. Gurgenes’ family members—Peranius, Pacurius, and Phazas—had careers in the Roman military.
Kavadh I gave his support to the communistic sect founded by Mazdak, who demanded that the rich should divide their wives and their wealth with the poor. His intention evidently was, by adopting the doctrine of the Mazdakites, to break the influence of powerful magnates from high classes such as the Wuzurgan. The Wuzurgan then sided with the Zoroastrian clergy, and in 496 had him deposed and incarcerated in the "Castle of Oblivion (Lethe)" in Susiana, and his brother Djamasp (496–498) was raised to the throne.
Kavadh, however, escaped and found refuge with the Hephthalites. In 498, with 30,000 troops from the Hephthalite king, and with the aid of Sukhra's son Zarmihr Karen, Kavadh became king again and punished his opponents. He also appointed Bozorgmehr, another son of Sukhra, as his minister. Kavadh then appointed his son, Kawus, as the governor of Padishkhwargar and gave him the title of Padishkhwargar Shah (king of Padishkhwargar).
In 529, Mazdak's doctrine was formally refuted in a theological discussion held before the throne of the king by the orthodox Magians, and its adherents were slaughtered and persecuted everywhere; Mazdak himself was hanged.
Kavadh needed money to pay his debts to the Hephthalites who had helped him regain his throne, and he applied for subsidies to the Byzantine Empire, which had before supported the Sasanians. But now the Emperor Anastasius I (491–518) refused subsidies, which made Kavadh try to gain the money by force.
In 502, Kavadh captured Theodosiopolis, perhaps with local support; the city was in any case undefended by troops and weakly fortified. Kavadh, along with Adergoudounbades, 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, although unsupported by troops, repelled the Persian assaults for three months before they were finally beaten. The Romans attempted to recapture the city, but they were unsuccessful. Kavadh then tried to capture Edessa in Osroene, but was unsuccessful.
In 505 an invasion of Armenia by the Huns from the Caucasus led to an armistice, during which the Romans paid subsidies to the Persians for the maintenance of the fortifications on the Caucasus, and in return for Amida, which was captured by Kavadh. The peace treaty was signed by Bawi, the brother-in-law of Kavadh.
In 524–525 , Kavadh proposed that Justin I adopt his youngest and favorite son, Khosrau, but the negotiations soon broke down. Kavadh then had Seoses, his negotiator, executed. Hostility between the two powers erupted into conflict when Guaram I, the king of Caucasian Iberia, defected to the Romans in 524–525, after Kavadh tried to convert the Iberians to Zoroastrianism. Sasanian and Roman fighting then broke out in the Transcaucasus region and upper Mesopotamia by 526–527. Kavadh's Arab vassal, al-Mundhir IV ibn al-Mundhir, laid waste to Mesopotamia and slaughtered the monks and nuns.
In 530, Kavadh sent Perozes and Baresmanas at the head of 50,000 men to capture Dara; the two generals, were, however, defeated and killed by the forces of Belisarius. In 531, the Persian general Azarethes managed to defeat Belisarius at the Battle of Callinicum. However, the Sasanian losses were so high that Kavadh removed Azarethes from his post.
Kavadh then organized another invasion of Byzantine territory, in which a large army, commanded by Mihr-Mihroe, Adergoudounbades and Bawi, invaded Mesopotamia and besieged the city of Martyropolis, which at that time was being protected by Buzes and Bessas. However, with winter approaching and Byzantine reinforcements coming from Amida and the sudden death of Kavadh, the Sasanians lifted the siege in November or December.
Kavadh I was succeeded by his youngest son Khosrau I; however, at the beginning of his reign in 531, Bawi, along with other members of the Persian aristocracy, became involved in a conspiracy in which they tried to overthrow Khosrau and make Kavadh, the son of Kavadh's second eldest son Zamasp (Zames), the king of the Sasanian Empire. Upon learning of the plot, Khosrau executed all his brothers and their offspring, along with Bawi and the other "Persian notables" who were involved. Khosrau also ordered the execution of Kavadh, who was still a child, and was away from the court, being raised by Adergoudounbades. Khosrau sent orders to kill Kavadh, but Adergoudounbades disobeyed and brought him up in secret, until he was betrayed to the shah in 541 by his own son, Bahram (Varranes). Khosrau had him executed, but Kavadh, or someone claiming to be him, managed to flee to the Byzantine Empire.