On 23 October 1086 the Almoravid emir Yusuf ibn Tashfin, allied with the taifa kings, crushed Alfonso VI of León and Castile near Badajoz — the battle known in Arabic as az-Zallaqah — halting the Christian advance after the fall of Toledo.
The Battle of Sagrajas, called az-Zallaqah in Arabic, was fought on 23 October 1086 near Badajoz between the Almoravid emir Yusuf ibn Tashfin, allied with the Muslim taifa kings, and Alfonso VI of León and Castile. It was a crushing Christian defeat that halted the advance opened by the fall of Toledo the year before.
The battle marked the entry of the Almoravids into Iberian affairs. Though Yusuf did not exploit his victory at once, Sagrajas ended the run of Christian success and set in motion the Almoravid takeover of al-Andalus.
Alfonso VI's capture of Toledo in 1085 terrified the taifa rulers, who realised they could not resist the Christian kingdoms alone. Al-Mutamid of Seville led an appeal to Yusuf ibn Tashfin, the emir who had forged the Almoravid empire in the Maghreb, even at the risk that the newcomer might turn on his hosts.
Yusuf crossed the strait with a disciplined army and united it with the taifa forces. Alfonso VI, styling himself emperor and at the peak of his power, advanced south to meet the combined host near Badajoz.
Yusuf commanded the hardened Almoravid regulars, supported by the levies of the taifa kings — a coalition of North African discipline and Andalusi manpower. Alfonso VI led the combined feudal host of León, Castile and their allies, confident after Toledo.
The figures given by the chroniclers are wildly inflated on both sides and cannot be used. What is certain is that Yusuf kept a strong reserve in hand while Alfonso committed his strength early — the difference that decided the day.
Alfonso opened with a powerful charge that scattered the taifa troops, and for a time the Christians seemed to be winning. But Yusuf had held his Almoravid regulars back, and threw them in when the Christians were committed and disordered, while a detachment struck Alfonso's camp in the rear.
Caught between the fresh Almoravid line and the assault on his camp, and unsettled — the sources say — by the din of Almoravid drums, Alfonso's army broke and was slaughtered. The king escaped with a small band, wounded, leaving the field to Yusuf.
The defeat stunned Christian Spain and ended the momentum of Alfonso's reign, but Yusuf drew back to Morocco on news of his son's death and did not press his advantage or besiege Toledo. In the short term little territory changed hands.
The deeper consequence was decisive: the Almoravids were now committed to al-Andalus. Returning in the 1090s, Yusuf deposed the taifa kings who had called him in and annexed Muslim Iberia to his empire, freezing the Reconquista for a generation.
Sagrajas is the classic example of how fragmented the "sides" of the Reconquista were: Muslim taifa kings, unable to face a Christian king, imported a North African power that then swallowed them, while the Christian coalition itself was a patchwork of feudal contingents. Religious labels conceal a tangle of rival interests.
It also punctures the idea of a steady Christian advance. The recovery of Toledo looked like a decisive breakthrough; within a year Sagrajas showed how quickly the balance could swing when a new power entered from Africa.