Villa, by contrast, was nearly illiterate and had never served in a professional army. However, he complemented his staff with Gen. Felipe Angeles, a capable career military officer. After defecting to Villa's División del Norte from Venustiano Carranza's Constitutionalist Army in March 1914, Angeles became one of Villa's most trusted military advisers. Unlike Villa, Angeles was more careful and calculating. Privately, he thought that Villa was often too rash in his decision making. Angeles' initial absence due to an injury while riding his horse would prove critical at the beginning of the Battle of Celaya.