The word Būya (Arabic Buwayh) is a Middle Persian name ending in the diminutive ـویه (Middle Persian -ōē, modern Persian -ūyeh,  Arabic -uwayh). The Buyids were descendants of Panah-Khusrow, a Zoroastrian from Daylam. He had a son named Buya, who was a fisherman from Lahijan, and later left Zoroastrianism and converted to Islam. Buya later had three sons, named Ahmad,  'Ali, and Hasan, who would later carve the Buyid kingdom together. Most historians agree that the Buyids were Daylamites. The Buyids claimed royal lineage from Bahram V, 15th king of the Sasanian Empire.

Rise (934-945)

The founder of the dynasty, 'Ali ibn Buya, was originally a soldier in the service of the Daylamite warlord Makan ibn Kaki, but later changed his adherence to the Iranian ruler Mardavij, who had established the Ziyarid dynasty, and was himself related to the ruling dynasty of Gilan, a region bordering Dailam. 'Ali was later joined by his two younger brothers, Hasan ibn Buya and Ahmad ibn Buya. In 932, 'Ali was given Karaj as his fief, and thus was able to enlist other Daylamites into his own army. However, 'Ali's independent actions made Mardavij plan to have him killed, 'Ali was informed of Mardavij's plan by the latter's own vizier. The Buyids brother, with 400 of their Daylamite supporters, then fled to Fars, where they managed to take control of Arrajan. However, the Buyids and the Abbasid general Yaqut shortly came into a struggle for the control of Fars, which the Buyids eventually emerged victorious in. This victory opened the way for the conquest of the capital of Fars, Shiraz.

'Ali also made an alliance with the landowners of Fars, which included the Fasanjas family, which would later produce many prominent statesmen for the Buyids. Furthermore, 'Ali also to enlist more soldiers, which included the Turks, who were made part of the cavalry. 'Ali then sent his brother Ahmad on an expedition to Kerman, but was forced to withdraw from them after opposition from the Baloch people and the Qafs. However, Mardavij, who sought to depose the Abbasid caliph of Baghdad and recreate a Zoroastrian Iranian Empire, shortly wrested Khuzestan from the Abbasids and forced 'Ali to recognize him as his suzerain.

Luckily for the Buyids, Mardavij was shortly assassinated in 935, which caused chaos in the Ziyarid territories, a perfect situation for the Buyid brothers; Ali and Ahmad conquered Khuzistan, while Hasan captured the Ziyarid capital of Isfahan, and in 943 captured Rey, which became his capital, thus conquering all of Jibal. In 945, Ahmad entered Iraq and made the Abbasid Caliph his vassal, at the same receiving the laqab Mu'izz ad-Dawla ("Fortifier of the State"), while 'Ali was given the laqab Imād al-Dawla ("Support of the State"), and Hasan was given the laqab Rukn al-Dawla ("Pillar of the State").

Height of power and Golden age (945-983)

In addition to the other territories the Buyids had conquered, Kirman was conquered in 967, Oman (967), the Jazira (979), Tabaristan (980), and Gorgan (981). After this, however, the Buyids went into a slow decline, with pieces of the confederation gradually breaking off and local dynasties under their rule becoming de facto independent.

Decline and fall (983-1048)

The death of Adud al-Dawla is considered the starting point of the decline of the Buyid dynasty; his son Abu Kalijar Marzuban, who was in Baghdad at the time of his death, first kept his death secret in order to ensure his succession and avoid civil war. When he made the death of his father public, he was given the title of "Samsam al-Dawla". However, Adud's other son, Shirdil Abu'l-Fawaris, challenged the authority of Samsam al-Dawla, resulting in a civil war. Meanwhile, a Marwanid chieftain named Badh, seized Diyabakr and forced Samsam al-Dawla to recognize him as the vassal ruler of the region. Furthermore, Mu'ayyad al-Dawla also died during this period, and he was succeeded by Fakhr al-Dawla, who with the aid of Mu'ayyad al-Dawla's vizier Sahib ibn 'Abbad became the ruler of Mu'ayyad al-Dawla's possessions. Another son of Adud al-Dawla, Abu Tahir, Firuzshah, established himself as the ruler of Basra and took the title of "Diya' al-Dawla", while another son, Abu'l-Husain Ahmad established himself as the ruler of Khuzistan, taking the title of "Taj al-Dawla".

Shirdil Abu'l-Fawaris (known by his title of "Sharaf al-Dawla") quickly seized Oman from Samsam al-Dawla, and in 983, the Turkic troops of Samsam al-Dawla mutinied against him, and left Iraq for Fars, but most of them were persuaded by his relative Ziyar ibn Shahrakawayh to stay in Iraq. However, Iraq was in grim affairs, and several rebellions occurred, which he however, managed to suppress, the most dangerous rebellion being under Asfar ibn Kurdawayh, who tried to make Abu Nasr Firuz Kharshadh (known by his title of "Baha' al-Dawla") the ruler of Iraq. During the same period, Samsam al-Dawla also managed to seize Basra and Khuzistan, forcing his two brothers to flee to Fakhr al-Dawla's territory.

During the mid-11th century, the Buyid amirates gradually fell to the Ghaznavid and Seljuq Turks. In 1029, Majd al-Dawla, who was facing an uprising by his Dailami troops in Ray, requested assistance from Mahmud of Ghazna.[35] When Sultan Mahmud arrived, he deposed Majd al-Dawla, replaced him with a Ghaznavid governor and ended the Buyid dynasty in Ray.

In 1055, Tughrul conquered Baghdad, the seat of the caliphate, and ousted the last of the Buyid rulers. Like the Buyids, the Seljuqs kept the Abbasid caliphate as the titular ruler.

The Buyids established a confederation in Iraq and western Iran. This confederation formed three principalities - one in Fars, with Shiraz as its capital - the second one in Jibal, with Ray as its capital - and the last one in Iraq, with Baghdad as its capital. However, during their late period, more principalities formed in the Buyid confederation. Succession of power was hereditary, with fathers dividing their land among their sons.

The title used by the Buyid rulers was amir, meaning "governor" or "prince". Generally, one of the amirs would be recognized as having seniority over the others; this individual would use the title of amir al-umara, or senior amir. Although the senior amīr was the formal head of the Būyids, he did not usually have any significant control outside of his own personal amirate; each amir enjoyed a high degree of autonomy within his own territories. As mentioned above, some of the stronger amirs used the Sassanid title of Shahanshah. Furthermore, several other titles such as malik ("king"), and malik al-muluk ("king of kings"), were also used by the Buyids. On a smaller scale, the Buyid territory was also be ruled by princes from other families, such as the Hasanwayhids.

Military

During the beginning of the Buyid dynasty, their army consisted mainly of their fellow Daylamites, a warlike and brave people of mostly peasant origin, who served as foot soldiers. The Daylamites had a long history of military activity dating back to the Sasanian period, and had been mercenaries in various places in Iran and Iraq, and even as far as Egypt. The Daylamites, during a battle, normally bore a sword, a shield, and three spears. Furthermore, they were also known for their formidable shield formation, which was hard to break through.

But when the Buyid territories increased, they began recruiting Turks into their cavalry, who had played a prominent role in the Abbasid military. The Buyid army also consisted of Kurds, who, along with the Turks, were Sunnis, while the Daylamites were Shi'i Muslims. However, the army of the Buyids of Jibal mainly composed of Daylamites.

The Daylamites and Turks often quarrelled with each other in an attempt to be the dominant force within the army.[44] To compensate their soldiers the Buyid amīrs often distributed iqtāʾs, or the rights to a percentage of tax revenues from a province (tax farming), although the practice of payment in kind was also frequently used. While the Turks were favoured in Buyid Iraq, the Daylamites were favoured in Buyid Iran.