Khuzestan Central Persia Caucasus Pars Khorasan Other geographies Ridda Wars Conquest of Sasanian Persia Conquest of Byzantine Syria Campaigns in Africa Campaigns in Armenia and Anatolia The Battle of Walaja (Arabic: معركة الولجة) was fought in Mesopotamia 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.

After the Ridda Wars a Muslim tribal chief raided the Persian frontier towns in Iraq.

It was important for Abu Bakr that his expedition did not suffer a defeat, for that would confirm and strengthen the fear of Sassanid military strength.

The commanders of the defeated Persian armies were said to be some of the most experienced and most highly regarded figures at the Sassanid court.

While having only sustained minor casualties, the Muslims had been able to defeat a large Sassanid army and to acquire a vast amount of booty.

The agents informed Khalid about the concentration of new Sassanid armies in the area of Walaja and their much greater numbers.

With an army of about 15,000 men, Khalid set off in the direction of Hira, moving at a fast pace along the southern edge of the great marsh.

A few days before Bahman was expected, Khalid's army arrived and camped a short distance from Walaja.

The Muslims faced two challenges, one strategic and one tactical: Khalid gave instructions to Suwaid bin Muqarrin to see to the administration of the conquered districts with his team of officials, and posted detachments to guard the lower Tigris against possible enemy crossings from the north and east, and to give warning of any fresh enemy forces coming from those directions.

[7] The battlefield consisted of an even plain stretching between two low, flat ridges, which were about 2 miles apart and 20 to 30 feet in height.

During this time, Khalid is said to have duelled with a Persian champion of gigantic proportions known as Hazar Mard (A Thousand Men) and killed him, which was a psychological victory for the Muslims.

At his command, the Sassanians, supported by the Persian heavy cavalry, carried out a general attack on the Muslim front.

On Khalid’s instructions the Muslim centre started retreating slowly and in order while the wings held the ground.

The main body of the Muslim army under Khalid ibn al-Walid resumed the attack against the Persian front, while at the same time extending its flanks to join with the cavalry and completely surround the Sassanids.

Recoiling from the assaults that came from all directions, the Sassanid army gathered in an unwieldy mass, unable to use their weapons freely.

After annihilating another army of the Sassanid Persians and their Christian Arab allies at the final Battle of Ullais, the Muslims conquered Hira, the capital city of Mesopotamia in late May 633.

In 634, Abu Bakr ordered Khalid ibn Walid to proceed to Syria with half of his army to command the invasion of the Byzantine Empire.

The Sassanids, under their new emperor Yazdgerd III, raised new armies and defeated the Muslims in the Battle of the Bridge, regaining some lost ground in Iraq.

The second invasion of Iraq was undertaken under Sa`d ibn Abī Waqqās who, after defeating the Sassanid army at the Battle of al-Qādisiyyah in 636, captured Ctesiphon.