Ka cika wannan jumla: Mutanen Espanya masu cin nasara da jagorancin
A shekara ta 1521, Hernán Cortés ya ci babban birnin Aztec na Tenochtitlan (a inda ake da birnin Mexico a yau) kuma ba da daɗewa ba bayan haka, a shekara ta 1524, 'yan mishan na Franciscan suka bi shi. Sahagún ba ya cikin wannan rukuni na farko na 'yan uwa goma sha biyu, waɗanda suka isa New Spain a 1524. Sahagún ya yi bayani, a cikin Mutanen Espanya da kuma Nahúatl, game da jayayya da waɗannan 'yan Franciscan suka yi a Tenochtitlan ba da daɗewa ba bayan isowarsu, a shekara ta 1564, don ya ba da misali ga masu wa'azi na gaba. Saboda iliminsa da kuma matsayinsa na addini, an zaɓi Sahagún a shekara ta 1529 ya shiga aikin wa'azi a New Spain. Zai yi shekara 61 a wurin.