The process of Portuguesification began under the reigns of kings Sancho I and Alfonso II. Yet it was the famous Christian victory over the Almohads at Navas de Tolosa (near Jaén) in 1212 - leaving 100,000 Moors dead - that would effectively secure this area of south-western Iberia, and establish a lasting peace. The São Mamede mountains and Guadiana valleys now became a bridgehead from which the reconquista could make strong inroads into Almohad territory in the Southern Alentejo, Algarve, Southern Extremadura and north-west Andalusia.