When Bhima went after Ashwatthama to punish him for attacking Panchal camp at night and killing all the survivors of Kurukshetra war including Draupadi's sons and brothers, Shrikrishna told Yudhishthira that they should not waste time and follow Bhima. Shrikrishna narrated this incident to tell them how dangerous Ashwatthama could be.

When Drona taught the supreme Brahmashira weapon to Arjuna, Ashwatthama insisted that he should also be given that knowledge. Drona could not refuse his only son and reluctantly taught him the method to invoke the destructive weapon. Drona knew about his sons temperament so he told him that he should never ever fire this weapon in battle specifically not on humans. Drona added that he was worried that his son would deviate from the path of Dharma.

During Pandava's exile Ashwatthama visited Dwaraka and lived there for some time. One day he approached Shrikrishna and told him that he had the knowledge of the supreme Brahmashira weapon which his father attained from rishi Agastya. He proposed to teach that to Shrikrishna in exchange for his Sudarshana Chakra. Shrikrishna pointed towards his bow, mace and Chakra and asked him to take whichever weapon he wanted. He didn't even need anything in return from Ashwatthama.

Ashwatthama jumped to pick up the Sudarshana Chakra with his left hand but he couldn't move it. He then tried with his right hand with same result. He tried his best but with all his energy he could not move it even an inch. Eventually he fell unconscious.

Finally when he gave up, Shrikrishna told him that Arjuna who was so dear to him and could ask him for anything had never ever asked for his Sudarshana. His dear son Pradyumna, who was a great warrior himself never asked for it. Even Balarama, Gada or Samba never asked for it. What prompted him to ask for his Sudarshana?

Ashwatthama replied that after taking his Sudarshana Chakra he wanted to fight him. He believed that he would become invincible once he possessed the divine disc.

Shrikrishna then told Yudhishthira and Arjuna that they should rush after Bhima and protect him from Ashwatthama who may be inclined to use Brahmashira in that situation.