The Caliphate of Córdoba was subsumed in a period of upheaval and civil war (the Fitna of al-Andalus) and collapsed in the early 11th century, spawning a series of ephemeral statelets, the "taifas". Until the mid 11th century, most of the territorial expansion southwards of the Kingdom of Asturias/León was carried out through a policy of agricultural colonization rather than through military operations; then, profiting from the feebleness of the taifa principalities, Ferdinand I of León seized Lamego and Viseu (1057–1058) and Coimbra (1064) away from the Taifa of Badajoz (at times at war with the Taifa of Seville); Meanwhile, in the same year Coimbra was conquered, in the Northeastern part of the Iberian Peninsula, the Kingdom of Aragon took Barbastro from the Hudid Taifa of Lérida as part of an international expedition sanctioned by Pope Alexander II. Most critically, Alfonso VI of León-Castile conquered Toledo and its wider taifa in 1085, in what it was seen as a critical event at the time, entailing also a huge territorial expansion, advancing from the Sistema Central to La Mancha. In 1086, following the siege of Zaragoza by Alfonso VI of León-Castile, the Almoravids, religious zealots originally from the deserts of the Maghreb, landed in the Iberian Peninsula, and, having inflicted a serious defeat to Alfonso VI at the battle of Zalaca, began to seize control of the remaining taifas.