The Battle of al-Qādisiyyah was a pivotal confrontation that occurred between the Rashidun Caliphate and the Sasanian Empire in Iraq. The two forces clashed around 636, with the battle site located near the banks of the Euphrates River. The Rashidun army, consisting of approximately 30,000 troops, was led by the notable commander Sa'd ibn Abi Waqqas. Opposing them was the Sasanian force, which was significantly larger and better equipped, commanded by Rustom Farrokhzad, a respected general in the Persian army.

The battle lasted for several days, with both sides experiencing heavy casualties. The Rashidun forces employed superior tactics, utilizing their cavalry effectively in flanking maneuvers and leveraging their knowledge of the terrain. Notably, the introduction of a Muslim archery unit was critical, as it caused considerable disarray within the Sasanian ranks. The result was a decisive victory for the Rashidun army, culminating in the fall of the Sasanian military establishment in the region. Following the battle, the sustained pressure from the Rashidun Caliphate opened the gates for further conquests in Persia, significantly expanding the reach of Islamic governance.

This victory not only marked the beginning of the end for the Sasanian Empire but also acted as a catalyst for the rapid spread of Islam beyond the Arabian Peninsula. The impact of the defeat resonated throughout Persia, further weakening the Sasanian hold and leading to the eventual establishment of Islamic governance over much of the former Sasanian territories in the subsequent years.