ALFONSO VIII of Castile’s victory in July 1212 reversed the thrust of half a century of peninsular history. Since the death of Alfonso VII in 1157 the kingdoms of León and Castile had been largely on the defensive, and at Alarcos in 1195 Christian Spain had experienced its worst military disaster in over a century, with casualties reportedly numbering 140,000 against a mere 500 of the ‘tremendous army’ of Muslims. The turning of the tables at Las Navas de Tolosa seventeen years later could scarcely have been more decisive: a death toll of 25 and 20,000 respectively, according to Archbishop Rodrigo Jiménez de Rada – who must have known because he was there, and who because he was a historian must have been telling the truth.

The cost of victory had been as spectacular as the outcome. In the months before the battle, Alfonso VIII’s recruiting sergeants at home and abroad had been offering to meet the expenses of all volunteers to Christendom’s cause. And although not that many came – at least not from abroad – the expense of Las Navas was, in Alfonso’s own words, ‘almost unbearable and onerous’. Twenty years on, the chronicler Bishop Juan of Osma confirmed this. The king had spent gold in the cause ‘like water’, distributing largesse as fast as his moneyers could supply coin. Of the three kingdoms to be considered in this chapter, Castile had by far the most extensive frontiers to defend, and the cost of doing so and of advancing the Christian reconquest of the peninsula was to cripple its kings throughout the thirteenth century and beyond, imposing strains on their realm with which their Navarrese and Portuguese neighbours were largely unfamiliar.