in common discussion and academia, despite its falling out of political use in the region. According to Ghulam Mohammad Ghobar, Afghanistan's current Persian-speaking territories formed the major portion of Khorasān, as two of the four main capitals of Khorasān (Herat and Balkh) are now located in Afghanistan. Ghobar uses the terms "Proper Khorasan" and "Improper Khorasan" in his book to distinguish between the usage of Khorasān in its strict sense and its usage in a loose sense. According to him, Proper Khorasan contained regions lying between Balkh in the east, Merv in the north, Sistan in the south, Nishapur in the west and Herat, known as the Pearl of Khorasan, in the center. 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. History Ancient era Before the region fell to Alexander the Great in 330 BC, it was part of the Persian Achaemenid Empire and prior to that it was occupied by the Medes. The land that became known as Khorasan in geography of Eratosthenes was recognized as Ariana by Greeks at that time, which made up Greater Iran or the land where Zoroastrianism was the dominant religion. The southeastern region of Khorasan fell to the Kushan Empire in the 1st century AD. The Kushan rulers built a capital in modern-day Afghanistan at Bagram and are believed to have built the famous Buddhas of Bamiyan. Numerous Buddhist temples and buried cities have been found in Afghanistan. However, the region of Khorasan remained predominantly Zoroastrian but there were also Manichaeists, sun worshippers, Christians, Pagans, Shamanists, Buddhists, Jews, Hindus and others. One of the three great fire-temples of the Sassanids "Azar-burzin Mehr" is situated near Sabzevar in Iran. The boundary of the region began changing until the Kushans and Sassanids merged to form the Kushano-Sassanian civilization. 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. Since the Sasanian territories were more or less remained stable up to Islamic conquests, it can be concluded that Sasanian Khorasan was bordered to the south by Sistan and Kerman, to the west by the central deserts of modern Iran, and to the east by