The Battle of Walaja (Arabic: معركة الولجة‎) was a battle fought in Mesopotamia (Iraq) in May 633 between the Rashidun Caliphate army under Khalid ibn al-Walid and Al-Muthanna ibn Haritha against the Sassanid Empire and its Arab allies. In this battle the Sassanid army is said to have been two times the size of the Muslim army. Khalid decisively defeated the numerically superior Sassanian forces using a variation of the double envelopment tactical manoeuvre, similar to the manoeuvre Hannibal used to defeat the Roman forces at the Battle of Cannae; however, Khalid is said to have developed his version independently.