Who defeated the Kushan empire?

The Kushan Empire fragmented into semi-independent kingdoms in the 3rd century AD. Their western half was taken over by the Sassanid Empire while their eastern territories fell to the Gupta Empire.

The last vestiges of the Kushan Empire were overwhelmed and defeated by the Hunnic tribes – Kidarites and the Hepthalites

For further reading check the following articles:

• Kushan Empire
• Gupta Empire
• Prehistoric Rock Paintings