Lord Krishna is the eighth avathaara (incarnation) out of Bhagavan Sri Vishnu’s ten avathaaras, also known a Dashaavathaara. This avathaara of Lord Vishnu has highest significance because it is in which he taught Srimad Bhagavad Geetha to Arjuna, which is revered as the holiest of literatures for all Hindus.
In the past, the demigods and demons had been at war in the heavens. When the demons were defeated by the demigods, they decided to instead attack this planet earth. Thus, they invaded the earth by discretely taking birth as princes in powerful royal families of the time.
And as the earth became overrun by militaristic activities of these kingly demons, the demigods including the Earth goddess earnestly sought Lord Vishnu’s protection. Seeing the deteriorating social and political conditions and hearing the prayers of the demigods, the all-compassionate Supreme Lord Sri Krishna decided to descend for the benefit of all.
Lord Krishna appeared in Dwapara Yuga (over five thousand years ago according to some calculations) in Mathura, India to Devaki and Vasudeva in the jail cell of the tyrant Kamsa. The place of His birth is known as Sri Krishna Janmasthana. He appeared with His brother Balarama in response to the demigods’ prayers for protection from the widespread influence of demonic administration on earth.
When Krishna and Balarama were older, they were invited to Mathura, where Kamsa, their demonic uncle, was planning their death in a wrestling match against two large and powerful wrestlers. When Kamsa saw his wrestlers defeated, he ordered his friends to drive the brothers out of Mathura, plunder the riches of their cowherd friends, and kill their fathers, Nanda and Vasudeva. However, Krishna immediately killed Kamsa. Balarama killed his eight brothers. Lord Krishna then established the pious King Ugrasena as the emperor of several kingdoms.
In Mathura, both Krishna and Balarama were initiated by Gargamuni in the Gayatri mantra. Later they went to live under the care of Sandipani Muni who instructed them in all the Vedic arts and sciences in sixty-four days and nights, especially in military science, politics and spirituality. As an offering (guru-daksina) to their teacher, they recovered his son from death. Although God does not need instruction from anyone else, Lord Krishna and his brother set the perfect example : one must accept instruction from and serve a bona-fide spiritual master to advance in spiritual life.
For the next eighteen years, they continued to live in Mathura halting the impending threat of many demonic kings. Later in their pastimes Lord Balarama married a princess named Revati. Lord Krishna married many queens, the foremost among them being the extraordinarily beautiftil Queen Rukmini. Both Krishna and Balarama established their palaces in Dvaraka off the coast of western India, where they enjoyed married life for many years. Although they were married, Lord Krishna and Lord Balarama exhibited the quality of detachment from material life perfectly.
When they were about ninety years old, the great world war of Kuruksetra took place. This climactic battle brought together all the major world leaders. Lord Krishna took the role of a charioteer on the side of the pious Pandavas, while Lord Balarama refusing to participate went on a pilgrimage tour thereby blessing the entire land of India.
At the start of the war, Lord Krishna displayed His stupendous Universal Form (Vishwa Roopa) delivered his famous message known as the Bhagavad Geetha, literally the song of God. This Song contains the essence of all knowledge having been spoken by the Supreme Lord Sri Krishna Himself. This war concluded with the destruction of the demonic kings and the reinstatement of the righteous Pandava princes.
The Supreme Lord descends from time to time in this material world to reestablish the teachings of the Vedas. In His Bhagavad Geetha, Lord Krishna promises: “Whenever and wherever there is a decline in religious practice, O descendant of Bharata, and a predominant rise of irreligion–at that time I descend Myself. To deliver the pious and to annihilate the miscreants, as well as to reestablish the principles of religion, I Myself appear milleniumm after millenium.”