Although it is not clear since when Mitsuhide made his mind to rebel, there is a view that he made his mind to rebel at the time of the party for renga (linked-verse) in the Atago-gongen Shrine before going to battle from the Kameyama-jo Castle by understanding the first line made by Mitsuhide, 'Tokihaima amegashitashiru satsukikana' (The time is now in May which everybody knows), as 'toki' means Mitsuhide himself, who belonged to the Toki clan which descended from the Minamoto clan and 'amegashitashiru' as 'to govern the area under the heaven,' namely governing the whole country.
光秀がいつ頃から謀反を決意していたかは明らかではないが、亀山城出陣を前にして、愛宕権現での連歌の会で光秀が詠んだ発句、「時は今　天が下知る　五月哉」は、「時（とき）」は源氏の流れをくむ土岐氏の一族である光秀自身を示し、「天が下知る」は、「天（あめ）が下（した）治る（しる）」、すなわち天下を治めることを暗示していると解し、この時点で謀反の決意を固めていたのだとする説もある。