of
Marwar - Folio from the Amber Album, . At the age of 10, Jai Singh became the Raja of Amber and the head of the
Kachhwaha Rajputs. His military career spans the full reign of
Shah Jahan and the first decade of Aurangzeb's reign. Jai Singh's military career began during the accession of Shah Jahan as the Mughal emperor in 1627. Taking advantage of the change in sovereigns, Jai Singh's commander in the Deccan,
Khan Jahan Lodi, rebelled with his Afghan followers. However, Jai Singh brought away his own army to the north and then joined the campaign to defeat the rebels. Jai Singh was made a commander of 4000 for his service. Jai Singh, attached to Abdullah Khan's division, pursued Khan Jahan Lodi after he fled to the Deccan, accompanied by some of his followers. In 1630, Jai Singh fought in the Battle of Bir against Jahan Khan Lodi. In the end, the Afghans were routed, the Mughals pursued them, and Lodi was killed by Madho Singh Hada.
Campaign against Bijapur and Gond kingdoms The following year, Jai Singh served in the expedition against the Sultanate of Bijapur under Asaf Jahan but their campaign was thwarted by the
Deccan famine of 1630–1632. In 1633, Jai led the Rajput vanguard in the second expedition against Parenda.
Shahaji was out on a raid near Daulatabad when he encountered a Mughal contingent. In the ensuing Battle of Parenda (1634), Shahaji was defeated and fled while being pursued by Jai Singh. Jadunath Sarkar states that Jai Singh captured "8,000 oxen loaded with provisions, arms, and rockets, besides 3,000 men" from the enemy. For this, he was made the commander of five thousand. In 1636 Shah Jahan organized a grand campaign against the
Deccan sultanates in which Jai Singh played a leading part, serving as the leader of the Rajput vanguard in the invasion of Bijapur. Later this same army was sent to campaign against the
Gond kingdoms. For his part in these successful ventures Jai Singh was promoted to the rank of five-hazari and given equal number of troops under his control and the Chatsu district in
Ajmer was added to his kingdom. By defeating the
Meo robber tribes in the north of Amber, Jai Singh further increased the size of his ancestral kingdom. In 1641 he subdued the rebellion of Raja Jagat Singh
Pathania of the hill-state of Mau-Paithan (
Himachal Pradesh). == Central Asian campaigns ==