Which empire was conquered by the Rashidun Caliphate after the death of Muhammad?

The Rashidun Caliphate rapidly expanded its territory after the death of Muhammad, most notably conquering the Sassanian Empire. This ancient Persian empire was a significant power at the time, stretching across modern-day Iran and parts of the Middle East. The defeat of the Sassanids at battles such as the Battle of Qadisiyyah in 636 AD marked a pivotal turning point, leading to the eventual fall of this great empire. Along with the Sassanian Empire, the Rashidun Caliphate also launched campaigns against the Byzantine Empire. Their military prowess was showcased during the conquests of territories such as Syria and Egypt, where battles like the Battle of Yarmouk in 636 AD solidified Muslim authority in these regions. This expansion not only spread Islam but also transformed the political landscape of the ancient world!