The Muslim geographer Ibn Hawqal, who visited the country in the middle of the 10th century, spoke of frequent revolts by Mozarab peasants employed on large estates, probably those of the ruling aristocracy. There is also substantial evidence that Mozarabs fought in the defence of the thaghr (front line fortress towns), participating in raids against Christian neighbours and struggles between Muslim factions. For instance, in 936, a significant number of Christians holed up in Calatayud with the rebel Mutarraf, only to be massacred in a desperate stand against the Caliphate forces.