Generally religious teachings are delivered in a calm location like a temple, a cave or a forest. Is there any significance of the Gita being delivered in a battlefield?
Today we need a philosophy to guide our footsteps, so that we can meet the challenges of developing the immense manhood and womanhood of India. It is that philosophy and spirituality that we get in the Gita. The message of the Gita was given on the tumultuous battlefield of Kurukshetra a few thousand years ago. The Gita alone represents such a philosophy. All other teachings were given in a temple, or a cave, or a forest.
Here the student and teacher, Arjuna and Sri Krishna, were remarkable personalities; they were warriors. And the teacher, Sri Krishna, was a man full of compassion, and endowed with universal vision. The Gita is thus a heroic message from a heroic teacher to a heroic pupil. Its universality makes it applicable to any human being anywhere in the world, to make him or her realize one's fullest human possibilities.
Reference: Universal Message of the Bhagavad Gita Vol. 1 by Swami Ranganathananda (p.12)