Complex sentence: Over much of Central Asia, speakers of Iranian languages were replaced by speakers of Turkic languages: according to the works of the Iranian historian Rashid al-Din, the Mongols killed more than 700,000 people in Merv and more than a million in Nishapur.
Split into simpler sentences: Over much of Central Asia speakers of Iranian languages were replaced by speakers of Turkic languages. According to the works of the Iranian historian Rashid al-Din, the Mongols killed more than 700,000 people in Merv and more than a million in Nishapur.