
In the 3rd century CE, the fragmentation of the Kushan Empire led to the formation of semi-independent states, vulnerable to the expanding Sasanian Empire (224–561 CE), which by 300 CE had annexed Afghanistan, establishing the Kushanshahs as vassal rulers. Sasanian control, however, was challenged by Central Asian tribes, causing regional instability and warfare.
The disintegration of Kushan and Sasanian defenses paved the way for invasions by the Xionites/Hunas from the 4th century onwards. Notably, the Hephthalites emerged from Central Asia in the 5th century, conquering Bactria and posing a significant threat to Iran, eventually overthrowing the last Kushan entities. Hephthalite dominance lasted about a century, characterized by continuous conflict with the Sasanians, who maintained nominal influence over the region.
By the mid-6th century, the Hephthalites faced defeat in territories north of the Amu Darya by the Göktürks and were overcome by the Sasanians south of the river. The Göktürks, led by ruler Sijin, secured victories against the Hephthalites at the battles of Chach (Tashkent) and Bukhara, marking a significant shift in the region's power dynamics.