During the much of the Middle Ages, Muslims achieved what is remembered as a golden age of knowledge. During these times of strife in Europe, many Muslim caliphs and Sultans gathered the ancient texts of great classical empires: such as the Caliphs of Andalusian Cordoba with Roman texts or the Anatolian Seljuk Sultans with Greek texts) and attempted to re-integrate this knowledge into their present time. During this time a Persian Muslim helped develop progress in algebra. The golden age of Islam ended with the Mongol invasions in the mid 13th century. 