Before the Kurukshetra war, Krishna offers Duryodhana and Arjuna a choice. One side may have his army. The other may have Krishna himself, “resolved not to fight on the field, and laying down my arms.” Arjuna chooses Krishna.
In the battle, Bhishma presses the Pandavas hard. In the Ganguli translation, Krishna jumps down from Arjuna’s chariot and rushes at Bhishma, whirling his discus. Arjuna stops him “with difficulty at the tenth step.”
In the critical edition of the text, Krishna’s weapon in this scene is a chariot wheel.