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The capture of Lisbon happened in 1094 when the Almoravids, led by Syr ibn Abi Bakr, invaded and captured Lisbon from the Castilians, defeating its ruler, Count Raymond.
History
During the winter of 1092-1093, the last ruler of Taifa of Badajoz, Al-Mutawwakil, made an alliance with Alfonso VI of León and Castile for help against the approaching Almoravids. Al-Mutawwakil gave the towns of Santarém, Lisbon, and Sintra. The King received the towns and handed them over to Raymond of Burgundy. However, the Christian control of these towns didn't last for long. In the winter of 1093-1094, the Almoravids general, Sir Ibn Abi Bakr, sent a campaign to remove Al-Mutawwakil from his power. His forces captured Badajoz and executed Al-Mutawwakil and his sons.
After his victory, Syr ibn Abi Bakr marched to Lisbon. Count Raymond attempted to advance; however, he was surprised and suffered a major defeat. After this, the Almoravids assaulted Lisbon fiercely, killing and capturing the majority of the Castilian garrison. Thus restoring the important bastion in November 1094.