The Mahabharata war was to start on the new moon day (amavasya). Arjuna was totally dejected and depressed on seeing the formations of Kaurava and Pandava armies a day prior to amavasya, i.e. Chaturdasi. Earlier, it was Arjuna himself who had insisted that they were ready to fight the battle with the Kauravas and said that Krishna should not go to the Kaurava court on a peace mission. The same Arjuna was very nervous when the war was actually to commence.
Krishna wanted to impart the knowledge of the Bhagavad Gita to Arjuna to instil courage and enthusiasm in him. But before imparting this knowledge, Krishna wanted to test Arjuna, to see whether he had total faith in Him.
