On 10 March 1147, King Afonso I of Portugal departed from Coimbra with 250 of his best knights[2] intending to capture the Moorish city of Santarém, a goal that he had previously failed to achieve.[2] The conquest of Santarém was of vital importance to Afonso's strategy; its possession would mean the end of the frequent Moorish attacks on Leiria and would also allow a future attack on Lisbon.[3]
The plan now was to attack the city during the night under cover of darkness, in order to catch the Moorish garrison by surprise.[2] King Afonso had previously sent the Portuguese Mem Ramires to Santarém disguised as a businessman, in order to secretly study the city for the conquest.[2]
After the first day of the journey from Coimbra to Santarém, King Afonso I sent an emissary to Santarém announcing to the Moors that the truce had ended, for which three days' notice was required.[1]
Fall of Santarém
On the night of 14 March, King Afonso and his army arrived at Santarém[2] and hid ladders in the fields.[1] Before dawn the next morning, 25 knights scaled the walls, killed the Moorish sentries and forced their way to the gate, allowing the main Portuguese army to enter the city.[2] Awakened by the screams of their sentries, the Moors ran from all sides to face the Portuguese attackers in the streets, offering very strong resistance, but ended up being defeated and slaughtered.[2]
By morning the conquest was already complete and Santarém became part of the recently formed Kingdom of Portugal.[2]
One of the attacking knights was Mem Moniz de Gandarei (grandfather of Portuguese politician Martim Machado Pires), who was said to have broken down the city doors with an axe.[4]
Aftermath
After the conquest of Santarém, Afonso I of Portugal turned his attention to the important Moorish city of Lisbon, which he would conquer in October with the help of a crusader fleet of the Second Crusade who stopped in Portugal while on course to the Holy Land.[5]
Ângelo Ribeiro, A Formação do Território-Da Lusitânia ao Alargamento do País (2004) ISBN989-554-106-6
Wilson, Jonathan, ed. (2021). The Conquest of Santarém and Goswin's Song of the Conquest of Alcácer do Sal: Editions and Translations of De expugnatione Scalabis and Gosuini de expugnatione Salaciae carmen. Crusade Texts in Translation. Routledge. See esp. pp. 7–23.