Yazdegerd III in the context of Shahriyar (son of Khosrow II)

The Sasanian dynasty (also known as the Sassanids or the House of Sasan), the last Persian lineage of rulers to achieve hegemony over much of Western Asia before Islam, ruled 224 CE–650 CE. the house of Sasan founded the Sasanian Empire of Iran, It began with Ardashir I, who named the dynasty in honour of his predecessor, Sasan.

The Shahanshah was the sole regent, head of state and head of government of the empire. At times, power shifted de facto to other officials, namely the spahbed. Upon the empire's conquest by the Islamic caliphate in 651, members of the imperial family fled in exile to China following the death of Yazdegerd III, where they would become accepted as members of the imperial court by Emperor Gaozong of Tang. Although there would be numerous attempts to invade Islamic Persia with Chinese support, this branch of Sasanids would remain in China indefinitely. Narsieh, grandson of Yazdegerd and last recorded Sasanid in China, would adopt the surname Li (李) in honor of the Chinese imperial family.

The Battle of Nahavand (Arabic: معركة نهاوند Maʿrakah Nahāwand, Persian: نبرد نهاوند Nabard-e Nahâvand), also spelled Nihavand or Nahawand, was fought in 642 between the Rashidun Muslim forces under An-Numan ibn Muqarrin and Sasanian army under King Yazdegerd III. Yazdegerd escaped to the Merv area, but was unable to raise another substantial army. The battle ended in a victory for the Rashidun Caliphate and the Sasanids consequently lost the surrounding cities including Spahan (Isfahan). The engagement resulted in a catastrophic defeat for the Sasanid forces and marks the end of organized Sasanid resistance. Thus opening the path for Islamic expansion into Persia and the subsequent religious transformation of the region.

The former Sasanid provinces, in alliance with Parthian and White Hun nobles, resisted for about a century in the region south of the Caspian Sea, even as the Rashidun Caliphate was replaced by the Umayyads, thus perpetuating the Sasanid court styles, Zoroastrian religion, and Persian language.

Narsieh (Middle Persian: 𐭭𐭥𐭮𐭧𐭩 Narseh; simplified Chinese: 泥涅师; traditional Chinese: 泥涅師; pinyin: Nìnièshī) was a Persian general who fled to the Tang dynasty with his father, Peroz III, son of Yazdegerd III, the last Sasanian emperor of Persia, after the Muslim conquest of Persia.

He was escorted back to Persia with a Chinese army led by Pei Xingjian in 679, in order to restore him to the Sasanian throne. Pei's primary objective, however, was to vanquish an insurgency led by Khan claimant Ashina Duzhi of a Tang protectorate, the Western Turkic Khaganate; the army stopped in Tokharistan after Pei Xingjian defeated the Turks. Concerned by the long route to Persia, Pei lost his interest in reinstalling Narsieh as the Persian king and left him in the Anxi Protectorate alone, although Narsieh was able to keep his many servants and a high quality of life. Minor Turkic chieftains in the region then pledged their loyalty to the Tang dynasty due to the defeat of Ashina. The overall result of Pei's expedition was a success for the Tang. Upon returning to China, Pei was appointed the minister of rituals and Great General of the Right Flank Guards.

The Khalaj (Bactrian: χαλασσ, romanized: Xalass; Persian: خلج‌ها, romanized: Xalajhâ) are a Turkic ethnic group who mainly reside in Iran. In Iran they still speak the Khalaj language, although most of them are Persianized.

Historically, the Khalaj who lived among Pashtuns were slowly Pashtunized. Due to this, the Khaljis of Delhi, originating from Khalaj migrants from Afghanistan into India, were often considered to be Pashtuns by other Turkic nobles. The Ghiljis, one of the largest Pashtun tribes, also derive their name from the Khalaj, and it is likely that the Khalaj initially formed the core of this tribe.

The Sasanian monarchs were the rulers of Iran after their victory against their former suzerain, the Parthian Empire, at the Battle of Hormozdgan in 224. At its height, the Sasanian Empire spanned from Turkey and Rhodes in the west to Pakistan in the east, and also included territory in what is now the Caucasus, Yemen, UAE, Oman, Egypt, Palestine, Israel, Lebanon, Syria, Jordan and Central Asia.

The Sasanian Empire was recognized as one of the main powers in the world alongside its neighboring arch rival, the Roman Empire for a period of more than 400 years. The Sasanian dynasty began with Ardashir I in 224, who was a Persian from Istakhr, and ended with Yazdegerd III in 651.

Rostam Farrokhzād (Persian: رستم فرخزاد) was a dynast from the Ispahbudhan family, who served as the spahbed ("military marshal") of the northwestern quarter (kust) of Adurbadagan under the Sasanian monarchs Boran (r. 630–630, 631–632) and Yazdegerd III (r. 632–651). Rostam is remembered as a historical figure, a character in the Persian epic poem Shahnameh ("Book of Kings"), and as a touchstone of many Iranian nationalists.