In 1275 he raised some troops to engage Marinid armies that had attacked Andalusia. On 21 October 1275 he tried to intercept a numerically superior Marinid army in the battle of Martos but was defeated and taken prisoner. He was killed and beheaded.
His body was recovered and buried in the Toledo Cathedral. Because of his heroic death, he was venerated by the people as a martyr and considered Blessed.
Sources
Fernández Serrano, Francisco (October 1979). La muerte y el epitafio de don Sancho de Aragón, hijo de Jaime I, 1275 (in Spanish). ISBN84-00-05009-6.