It is said they have been carried out after Isshi-no-hen (the Murder in the Year of Issi (one of the 60 Oriental Zodiacs)) where Emperor Tenchi (latter-day Emperor Tenchi) assassinated SOGA no Iruka and destroyed the head family of Soga clan (this assassination case is sometimes referred to as the Taika Reforms).
天智天皇（後の天智天皇）らが蘇我入鹿を暗殺し蘇我氏本宗家を滅ぼした乙巳の変（いっしのへん）の後に行われたとされる（この暗殺事件を大化の改新と呼ぶこともある）。