In ancient times, simple yajóas used to play an important role in inner refinement and self-purification. The mahayagyas used to be performed to purify the social life. But, when the need for complete renovation of the nation (Rashtra) and that of the environment was felt, there was a tradition of Aïvamedha yagyas at the universal level. Thus, the yagyas have been classified into three categories; viz, yagya, mahayagya and Ashvamedha yagya. The magnitude of their results also increases in the same order.The rewards of Ashvamedha yagya are far more purifying. In the medieval period, Ashvamedha was thought to be the war for the expansion of the empire, whereas it used to be a special mahayagya performed for the benefit of the society and the nation, in the earlier ages.