 However, the names of the Muslim engineers were given by Muslim sources as Talib and his sons Abubakr, Ibrahim, and Muhammad, respectively by Chinese sources as Ala-ud-Din and Isma'il.Moreover, it has been claimed the siege had already ended before Marco Polo's arrival in China.Political infighting among the Song also contributed to the fall of Xiangyang and Fancheng; due to the power of the Lü family, many questioned their allegiance to the Song.