The Wall That Broke a Caliphate

In the 720s the Umayyad Caliphate had every reason to think nothing could stop it.

What one generation had done

Crossed the Strait of Gibraltar and overrun most of Iberia.

Pushed deep into Central Asia.

And in 712, under the young general Muhammad bin Qasim, taken Sindh - folding the Indus valley into the empire's eastern frontier.