The great Raja Man Singh of Amber had many sons, the most capable of whom were the eldest Jagat Singh and Bhau Singh. Jagat died even before his father and left behind a son Maha Singh. Following the Hindu custom of primogeniture, on Man Singh's death this grandson Maha Singh will be the successor or the next Raja of Amber. However the Mughal Emperor Jahangir declared Maha's uncle Bhau Singh to be more able and experienced, thus making him Raja in 1614 with the rank of a commander of 4000 (cavalry).
During the same time, to ensure that Maha Singh would not take the option of arms to impose his hereditary claim, he was also made a chief of 1000 and was given the Central Indian district of Garha as his estate. After some time he too received the title of Raja, but while serving the Deccan wars, Maha Singh died of excessive drinking in 1617. His uncle Bhau Singh died childless, and due to the same cause in 1621. At the young age of 10, Mirza Raja Jai Singh became the Raja of Amber and the head of the Kachwaha Rajputs. His military career extended the full control of Shah Jahan and the first half of Aurangzeb's reign.
Mirza Raja Jai Singh's first step towards the rise of prominence took place on the succession of Shah Jahan (1627). Thus, taking the advantage of this change of sovereigns, Mirza Raja Jai Singh's commander in the Deccan, Khan Jahan Lodi rebelled along with his Afghan followers. But the Rajput prince brought away his own army towards the north and then combined in the campaign that at last defeated the rebels. For these exclusive services Mirza Raja Jai Singh was made a commander of 4000.
In 1636 Shah Jahan organized a grand campaign against the southern sultanates in which Mirza Raja Jai Singh played a vital role. Later this same army was sent to campaign against the Gond kingdoms. For his part in these successful ventures Mirza Raja Jai Singh was promoted to the higher rank of commander of 5000 and the district of Chatsu in Ajmer was added to his kingdom. By defeating the Meo robber tribes in the north of Amber, Mirza Raja Jai Singh further amplified the size of his ancestral kingdom. In 1641 Mirza Raja Jai Singh subdued the rebellion of Raja Jagat Singh Pathania of the hill-state of Mau-Paithan in Himachal Pradesh.
In 1638 the Persian commander Ali Mardan Khan surrendered the fort of Kandahar to Shah Jahan. The emperor's son Shuja, accompanied by Mirza Raja Jai Singh, was sent to take liberation of this important fort. To frighten the Persian Shah from interfering in this task, Shah Jahan gathered a 50,000 strong army in Kabul. On this occasion Mirza Raja Jai Singh received the exclusive title of Mirza Raja from Shah Jahan, which had earlier honored his great-grandfather Raja Man Singh I of Amber by Emperor Akbar.
In 1647 Mirza Raja Jai Singh joined in Shah Jahan's invasion of Balkh and Badakshan, located in Central Asia. The Mughals easily achieved the conquest but the occupation of these poor regions could not be sustained and not even a single Mughal officer agreed to be posted permanently in that desolate land and away from the assets and luxury of India, which was satirical since many of them had originated from these parts of the world itself. This impractical project thus ended in financial failure. In 1649 another severe blow knocked down Mughal prestige. Shah Abbas II recovered Kandahar. The Mughals attempted twice to expel the Persians from Kandahar under the command of Prince Aurangzeb on both occasions Mirza Raja Jai Singh was present as an army commander, but the attempts did not attain success due to the lack of adequate artillery and poor marksmanship of the Mughal gunners.
Mirza Raja Jai Singh was sent again with this army at the third grand attempt in 1653 under the command of Shah Jahan's oldest and favorite son Dara Shikoh, who was a deadly rival of Aurangzeb. Prince Dara was knowledgeable in spiritual matters and was very secular in his outlook, but his military ineffectiveness and his flattering and imprudent advisers spoiled these noble qualities. Dara was predominantly harsh on officers that had taken part in the earlier campaigns under Aurangzeb and repeatedly teased Mirza Raja Jai Singh for those failures. But when his own campaign ended with the similar result, the Mughals finally gave up all attempts to recover Kandahar.
Dara however continued his aggression towards Mirza Raja Jai Singh on return to Agra and no promotions or awards were given to the expert general for competently covering the army's retreat. Instead Jaswant Singh of the rival Rathor clan was appointed as the commander of 6000 and received the superlative title of Maharaja. In 1657 Shah Jahan fell seriously ill, to the extent that he was even injured. While facing terrible dangers, Dara Shikoh now remembered Mirza Raja Jai Singh and the Rajput chief was made commander of 6000 and sent them eastwards along with Dara's son Sulaiman and the Afghan general Diler Khan.
Mirza Raja Jai Singh along with Sulaiman and others triumphed over Shuja at the Battle of Bahadurpur and chased him back to Bengal. By that time Aurangzeb had won the Battle of Dharmat and the Battle of Samugarh and had already captured Agra. Mirza Raja Jai Singh and his men were trapped far in the east while their homes and families in the west were at the pity of Aurangzeb's troops, thus Diler Khan advised Sulaiman to run away while they submitted to the new emperor.
After some more victories, Mirza Raja Jai Singh acquired the highest-ranking general and received rich gifts in gold and silver. Both his sons, Ram Singh and Kirat Singh, were raised in rank. The latter was serving under his father while the former was acting as his agent at the Mughal court.
Mirza Raja Jai Singh's invasion of Bijapur started in December 1665 and he had an army of 40,000 to which Shivaji added 2000 cavalry and 7000 infantry. During this invasion, Mirza Raja Jai Singh was punished harshly, partly because he was also held responsible for his son's actions at Agra, and partly because he was a Hindu. For the operating cost of this campaign the Rajput general had received only 3 million rupees from Aurangzeb, and had already spent 10 million rupees from the gathered troops in his ancestral kingdom. His master compensated not a single part of his money. Only two years after Jai Singh's downfall Aurangzeb passed an order (1669) calling for the destruction of Hindu temples in the Mughal provinces.
Mirza Raja Jai Singh died in the Deccan on 28 August 1667 under mysterious circumstances. It is believed among the Rajputs that he had been poisoned by order of Aurangzeb. The fortunes of his family declined in the next two generations, but were revitalized and raised to astonishing heights by Jai Singh II.