History of Lord Krishna:
Lord Krishna appeared over five thousand years ago 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.
Previously, 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 Visnu'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.
The Supreme Lord descends from time to time in this material world to reestablish the teachings of the Vedas. In His Bhagavad-gita, 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." Although eternal the Lord appears in specific circumstances out of mercy for His devotees. In fact, His principal biography, the Srimad Bhagavatam states, "the learned men describe the births and activities of the Unborn and Inactive." Therefore, although He appears within the material dimensions of time and space, He is most definitely not of it.
Historically, Lord Krishna appeared on the midnight of the 8th day of the dark half of the month of Sravana. This corresponds to July 19th 3228 BC. He exhibited His pastimes for a little over 125 years and dissappeared on February 18th 3102 BC on the new moon night of Phalguna. (His departure marks the beginning of the current age of corruption known as Kali.)
The great scholar Srila Vishvanatha Chakravarti neatly outlines Lord Krishna's activities in this way: the first three years and four months were spent in Gokula, then equal lengths of time in Vmdavana and Nandagram, eighteen years and four months in Mathura, and finally ninety-six years and eight months in Dvaraka totalling 125 years of manifest pastimes. See the Krishna-lila chart.
Lord Krishna's early pastimes are briefly summarized at the website Krishna's Adventures in Vraja"During this childhood time , He grew up as the son of His foster parents Nanda and Yasoda in the midst of the idyllic beauty of Gokula, Vrindavana, and Nandagram. Not only did He destroy numerous demons, but also performed His famous rasa dance.
Krishna enjoyed the dance of love (rasa-lila) with the gopis many of whom are expansions of His own internal energies. The supreme gopi known as Srimati Radharani is the object of Krishna's highest devotion. This beautiful dance would occur in the autumn season at night under a full moon when Lord Krishna would captivate the young gopis with the extraordinary music of His flute . These esoteric pastimes constitute the most confidential expression of divinity ever revealed. 
Usually the conception of sprirtual perfection consists of overwhelming feelings only of awe and reverence at God's majesty. However, in these pastimes each devotee loves God either as a master, a best freind, a mischievous son, or even as an intimate lover, thus revealing the infinite possibilities of divine love. These early pastimes of Lord Krsna in Vrindavana illustrate the extraordinary intimacy that one can have with God. These pastimes are described in detail by Sri Visvantha Chakravarti in his Sri Krishna Bhavanamrta Mahakavya 
When Krsna and Balarama were older, They were invited to Mathura, where Karnsa, 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 and 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 Krsna 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 Krsna married many queens, the foremost among them being the extraordinarily beautiftil Queen Rukmani. (See Sri Rukmani website for the story of Their marriage). Both Krishna and Balarama established Their palaces in Dwaraka off the coast of western India, where They enjoyed married life for many years. Although They were married, Lord Krishna and Lord Balrama 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 Krsna 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 delivered His famous message known as the Bhagavad-gita, 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.
Having completed Their mission, Balarama and Krsna resumed Their life in Dvaraka where They spent some thirty-five more years before ending Their earthly manifest activities The foremost description of Lord Krishna's activities occurs in the Srimad Bhagavatam, literally "the Beautiful Book of God."Story2:
Who is Sri Krishna? Krishna is God, the Supreme Personality of Godhead. This fact is stated and corroborated in the Vedic scriptures and by various authorities. Lord Brahma in Brahma Samhita says, "Krishna who is known as Govinda is the Supreme Godhead. He has an eternal blissful spiritual body. He is the origin of all. He has no other origin and He is the prime cause of all causes" (BS 5.1). In the Bhagavata Purana Krishna becomes the chief object of devotion. After describing various incarnations of the Lord such as Rama, Balarama, Vamana, Nrsimha, and Vishnu, Srila
Sukadeva Goswami states, "All of the above mentioned incarnations are either plenary portions or portions of the plenary portions of the Lord, but Lord Krishna is the original Personality of Godhead" (SB 1.3.28). Lord Shiva in Gita Mahatmya, states that "only one God - Krishna, the son of Devaki" (Verse 7). In the Padma Purana it is stated, "By scrutinizingly reviewing all the revealed scriptures and judging them again and again, it is now concluded that Lord Narayana is the Supreme Absolute Truth, and thus He alone should be worshipped". Similarly it is said in the Skanda Purana, "In the material world, which is full of darkness and dangers, combined with birth and death and full of different anxieties, the only way to get out of the great entanglement is to accept loving transcendental devotional service to Lord Vasudeva. This is accepted by all classes of philosophers". The position of Krishna as God is confirmed by great personalities like Narada, Asita, Devala, Vyasa, Parasara, Brahma and Shiva. Finally Krishna Himself confirms this fact in the Bhagavad-gita to His friend and devotee, Arjuna. He clearly says that He is "the Supreme Lord of all planets and demigods" (BG 5.29), that "there is no truth superior to Me" (BG 7.7) and - "I am the source of all spiritual and material worlds. Everything emanates from Me" (BG 10.8).
What is the position of Krishna?
As God, there is no one equal to or greater than Krishna. He is the original, unborn, eternal person, the most ancient, completely independent, and the cause of all causes. Parasara Muni, the father of Srila Vyasadeva and a great scholar who had himself held the position of Vyasa in a previous kalpa, very nicely defines the position of Bhagavan (God) as one Who is complete in six kinds of opulence namely - wisdom, beauty, fame, power, wealth and renunciation. While there are many great personalities who are very famous or very wealthy, only Krishna as God is replete in all six opulence. The scriptures not only give us the unique position of Krishna but also give us a detailed description of all His aspects. They tell us that above this temporary material universe is an eternal spiritual world called Vaikuntha, and Krishna lives in the topmost planet of this universe called Goloka Vrindavana which is full of palaces made of touch-stone (cintamani), with trees that are capable of fulfilling all desires (kalpa-vraksha) and cows that are called Surabhi
Here Krishna eternally resides, served by hundreds and thousands of goddesses of fortune. He sports with His most confidential and intimate devotees, headed by Srimati Radharani. He has a form just like us but His body is spiritual and thus eternal. His complexion is dark-blue, like that of a rain-filled cloud and His eyes are like lotus petals. He is ever youthful, full of bliss and His beauty excels that of thousands of cupids. He likes to play the flute, He sports a crown with a peacock feather and He is adorned by the exquisite kastuba jewel. What is Krishna avatar?
In Chaitanya-charitamrita (2.20.263-264) it is stated that the "avatar, or incarnation of Godhead, descends from the kingdom of God for creating and maintaining the material manifestation. And the particular form of the Personality of Godhead who so descends is called an incarnation, or avatar. Such incarnations are situated in the spiritual world, the kingdom of God. When They descend to the material creation, They assume the name avatar." The Srimad Bhagavatam states that there are countless incarnations just like the waves of the oceans. They fall in various categories like lila (pastime), yuga (period of yuga), manavantara (period of Manu), purusa (Vishnu expansions) and shaktivesa (empowered). These avatars perform various pastimes based on the time, place and circumstances, but their purpose is always the same - "to attract the conditioned souls back to their eternal spiritual abode". The incarnations emanate from Vishnu. Maha-Vishnu is the original cause of all material creation and from Him Garbhodakashai-Vishnu expands and then Ksirodakasayi-Vishnu.
. Generally all incarnations appearing within the material world are plenary portions of Ksirodakasayi-Vishnu (also known as Hari). However only once in a day of Lord Brahma (which lasts for 4.32 billion of our years), does Krishna descend in His original form, as the avataree, the cause of all avatars. When Krishna appears all the incarnations join with Him. The Supreme Personality of Godhead is the complete whole and all the plenary portions and incarnations always live with Him. So when Krishna appeared, Lord Vishnu was always with Him, and while Krishna enjoyed His pastimes in Vrindavan, the killing of the demons was actually carried out by the His Vishnu portion. Since Krishna eternally resides in Vrindavan, when He left Vrindavan at the age of ten, it was His Vasudeva expansion that actually left.
Appearance of Krishna
In the era of the Svayambhuva Manu, prajapati Sutapa and his wife Prsni were instructed by Lord Brahma to have progeny. They performed severe austerities for twelve thousand years of the demigods to have the Lord as their child. Pleased by their austerities the Lord appeared and granted them this benediction. Since He gave them this benediction three times, in Satya-yuga He first appeared as the son of Prsni and Sutapa and was called Prsnigarba. In Treta-yuga they were Aditi and Kasyapa Muni and the Lord appeared as Vamanadeva. Finally in the Dvapara yuga, Krishna in His original form, appeared as the child of Devaki and Vasudeva. Krishna appeared specifically on the request of Bhudevi, the presiding deity of the Earth planet. Distressed by the burden of many demons who had appeared as powerful Kshatriyas and were ruling the planet impiously, she assumed the form of a cow and pleaded to Lord Brahma for help. Lord Brahma with all the demigods prayed to Lord Vishnu in Svetadvipa by chanting the Purusa-sukta prayers. At this time the Lord informed Brahma that in order to establish religiosity and destroy evil, He would soon appear as His original Self. In the meantime the various demigods were instructed to take birth in various families in the Yadu dynasty and prepare for the appearance of the Lord.
In the era of the Svayambhuva Manu, prajapati Sutapa and his wife Prsni were instructed by Lord Brahma to have progeny. They performed severe austerities for twelve thousand years of the demigods to have the Lord as their child. Pleased by their austerities the Lord appeared and granted them this benediction. Since He gave them this benediction three times, in Satya-yuga He first appeared as the son of Prsni and Sutapa and was called Prsnigarba. In Treta-yuga they were Aditi and Kasyapa Muni and the Lord appeared as Vamanadeva. Finally in the Dvapara yuga, Krishna in His original form, appeared as the child of Devaki and Vasudeva. Krishna appeared specifically on the request of Bhudevi, the presiding deity of the Earth planet. Distressed by the burden of many demons who had appeared as powerful Kshatriyas and were ruling the planet impiously, she assumed the form of a cow and pleaded to Lord Brahma for help. Lord Brahma with all the demigods prayed to Lord Vishnu in Svetadvipa by chanting the Purusa-sukta prayers. At this time the Lord informed Brahma that in order to establish religiosity and destroy evil, He would soon appear as His original Self. In the meantime the various demigods were instructed to take birth in various families in the Yadu dynasty and prepare for the appearance of the Lord.
Lifeline of Krishna
Historically, Lord Krishna appeared in the Dvapara yuga, on the midnight of the 8th day of the dark half of the month of Sravan. This corresponds to July 19th 3228 BC. He exhibited His pastimes for a little over 125 years and disappeared on February 18th 3102 BC on the new moon night of Phalgun. His departure marks the beginning of the current age of corruption known as Kali. The great scholar Srila Vishvanatha Chakravarti neatly outlines Lord Krishna's activities in this way. He was born in Mathura in the prison cell of Kamsa and carried to Gokul. The first three years and four months were spent in Gokula, then equal lengths of time in Vrindavan and Nandagram. At the age of eleven He left Vrindavan for Mathura where He lived for eighteen years and four months, and finally ninety-six years and eight months in Dvaraka totaling about 126 years of manifest pastimes. At the time of Mahabharata, when Krishna spoke the Bhagavad-gita, He was about ninety years of age. 
