In Sassanid times, the region became a major cultural center due to the wealth derived from the Northern Silk Road. Sassanid rule was interrupted by the Hephthalite invasion at the end of the 5th century and didn't return to the Sassanids until 565. Many Persian nobles and landlords escaped to this region after the Muslim conquest of Persia. It was also ruled by Göktürks until the Arab conquest between 705 and 715, the area became known as "Mā warāʼ al-Nahr" (Arabic, 'what is beyond the river'), sometimes rendered as "Mavarannahr".