Shreemad Bhagwad Geeta known as Yatharth Geeta is very beautifully compiled and interpreted by Paramhans Swami Adgadanand. It is expressed in the best possible allegoric way. Symbolizing each and every character of Mahabharata.
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He states the following about Ashwatthama:
अश्वत्थामन्, Aśvatthāman means the horse-voiced.
At the time of his birth, he neighed like the (celestial) steed Ucchaihsravas.
Drona, obedient to the injunctions of his father and moved by the
desire of offspring married Kripi, the daughter of Saradwat. And this
woman, ever engaged in virtuous acts and the Agnihotra, and the
austerest of penances, ...