The Pandavas were very angry with Ashvattama, Dronacharya's son, for setting their camp on fire. When Ashvattama saw the Pandavas approaching , he picked up straw and ordered it to go and kill the baby of Abimanyu and Uttara , who was still in Uttara's womb. The straw took the form of a sword. When Krishna saw the sword coming towards Uttara, he diffused its power and saved Uttara and her baby.