Greater Khorasan[2] (Middle Persian: 𐬒𐬊𐬭𐬀𐬯𐬀𐬥, romanized: Xwarāsān; Persian: خراسان, [xoɾɒːˈsɒːn] ⓘ) is a historical eastern region in the Iranian Plateau in West and Central Asia that encompasses western and northern Afghanistan, northeastern Iran, the eastern halves of Turkmenistan and Uzbekistan, western Tajikistan, and portions of Kyrgyzstan and Kazakhstan.

[7][8] The name was first given to the eastern province of Persia (Ancient Iran) during the Sasanian Empire[9] and was used from the late Middle Ages in distinction to neighbouring Transoxiana.

[3] Khorasan was first established as an administrative division in the 6th century (approximately after 520) by the Sasanians, during the reign of Kavad I (r. 488–496, 498/9–531) or Khosrow I (r. 531–579),[16] and comprised the eastern and northeastern parts of the empire.

[24] By the 10th century, Ibn Khordadbeh and the Hudud al-'Alam mentions what roughly encompasses the previous regions of Abarshahr, Tokharistan and Sogdia as Khwarasan proper.

[25][21][5]By the late Middle Ages, the term lost its administrative significance, in the west only being loosely applied among the Turko-Persian dynasties of modern Iran to all its territories that lay east and north-east of the Dasht-e Kavir desert.

[citation needed] Many Tajiks regard Khorasan as an integral part of their national identity, which has preserved an interest in the term, including its meaning and cultural significance, both in common discussion and academia, despite its falling out of political use in the region.

Improper Khorasan's boundaries extended to as far as Hazarajat and Kabul in the east, Baluchistan in the south, Transoxiana and Khwarezm in the north, and Damghan and Gorgan in the west.

[27]During the Sasanian era, likely in the reign of Khusrow I, Persia was divided into four regions (known as kust Middle Persian), Khwārvarān in the west, apāxtar in the north, nīmrūz in the south and Khorasan in the east.

[citation needed] The last Sassanid king of Persia, Yazdgerd III, moved the throne to Khorasan following the Arab invasion in the western parts of the empire.

[citation needed] The first kingdom independent from Arab rule was established in Khorasan by Tahir Phoshanji in 821, but it seems that it was more a matter of political and territorial gain.

[30] Other major independent dynasties who ruled over Khorasan were the Saffarids from Zaranj (861–1003), Samanids from Bukhara (875–999), Ghaznavids from Ghazni (963–1167), Seljuqs (1037–1194), Khwarezmids (1077–1231), Ghurids (1149–1212), and Timurids (1370–1506).

"[31] Throughout the nineteenth and twentieth century, the majority of Islamic archaeological efforts were focused on the medieval era, predominantly in areas near what is today Central Asia.

[citation needed] In particular, the Turgesh under the leadership of Suluk, and Khazars under Barjik clashed with their Arab neighbours in order to control this economically important region.

Julius Wellhausen wrote of him that "His age did not affect the freshness of his mind, as is testified not only by his deeds, but also by the verses in which he gave expression to his feelings till the very end of his life".

[35] In 724, immediately after the rise of Hisham ibn Abd al-Malik (r. 724–743) to the throne, Asad's brother Khalid al-Qasri was appointed to the important post of governor of Iraq, with responsibility over the entire Islamic East, which he held until 738.

[38][39] From the early days of the Muslim conquests, Arab armies were divided into regiments drawn from individual tribes or tribal confederations (butun or ‘asha‘ir).

Despite the fact that many of these groupings were recent creations, created for reasons of military efficiency rather than any common ancestry, they soon developed a strong and distinct identity.

[citation needed] By the 8th century, this division had become firmly established across the Caliphate and was a source of constant internal instability, as the two groups formed in essence two rival political parties, jockeying for power and separated by a fierce hatred for each other.

[citation needed] In the interim, the sources report variously that the province was run either by the Syrian general Ja'far ibn Hanzala al-Bahrani or by Asad's lieutenant Juday' al-Kirmani.

This province was part of the Iranian world that had been heavily colonised by Arab tribes following the Muslim conquest with the intent of replacing Umayyad dynasty which is proved to be successful under the sign of the Black Standard.

[52] It has produced scientists such as Avicenna, Al-Farabi, Al-Biruni, Omar Khayyam, Al-Khwarizmi, Abu Ma'shar al-Balkhi (known as Albumasar or Albuxar in the west), Alfraganus, Abu Wafa, Nasir al-Din al-Tusi, Sharaf al-Dīn al-Ṭūsī, and many others who are widely well known for their significant contributions in various domains such as mathematics, astronomy, medicine, physics, geography, and geology.