From 1342 to 1344, King Alfonso XI of Castile laid siege to the Marinid-held port of Algeciras, one of the most important naval bases in the Strait of Gibraltar. The siege was notable for the early use of gunpowder artillery and the involvement of Genoese and Portuguese naval forces. Alfonso's victory in 1344 marked a major Christian triumph in the Reconquista, seriously weakening Marinid power in Iberia.

The Siege of Algeciras was a popular subject for Castilian ballads and chronicle poetry, celebrating Alfonso XI as a crusading hero. It also appears in the poetry of the period as a symbol of Christian unity against Islam. The siege's narrative of technological innovation and strategic cunning influenced later epic poems about the Reconquista, including the 'Poem of Alfonso XI'.