The Muslim conquests of Afghanistan began during the Muslim conquest of Persia as the Arab Muslims migrated eastwards to Khorasan, Sistan and Transoxiana. Fifteen years after the Battle of Nahāvand in 642 AD, they controlled all Sasanian domains except in Afghanistan. Fuller Islamization was not achieved until the period between 10th and 12th centuries under Ghaznavid and Ghurid dynasty's rule who patronized Muslim religious institutions.
Khorasan and Sistan, where Zoroastrianism was well-established, were conquered. The Arabs had begun to move towards the lands east of Persia and in 652 AD they captured the city of Herat, establishing an Arab governor there. The Muslim frontier in modern Afghanistan had become stabilized after the first century of the Lunar Hijri calendar as the relative importance of the Afghan areas diminished. From historical evidence, it appears Tokharistan (Bactria) was the only area heavily conquered by Arabs where Buddhism fl