‘Yato dharma, tato jaya’ – wherever there is dharma, there is victory. Dharma means to do one’s duty selflessly; not just for oneself but for the good of people at large. This is the underlying theme of all Hindu scriptures. In Mahabharat it is explained more explicitly.
This message is presented as the central story in Mahabharat. It is a story of conflict between two families, the Kauravs and Pandavs, who had a common grandfather, Sage Vyas, incidentally the author of the epic himself. The ongoing conflict between the cousins takes them to the battlefield of Kurukshetra.