Brigadier Rajinder Singh was born on 14 June 1899, in Bagoona village, 35 km east of Jammu city in Samba Tehsil. Almost a century ago, his ancestor General Baj Singh, who served under Maharaja Gulab Singh, made the supreme sacrifice of fighting the enemy to his last breath in defence of Chitral. His grandfather, Hamir Singh, was a war veteran who had seven battle scars on his body. His father Subedar Lakha Singh had also served the motherland as a loyal soldier. Due to the untimely death of his father, Rajinder Singh was brought up under the care of his uncle, Lt. Colonel Govind Singh, since he was just six months old.
Rajinder Singh grew up to be a sober, studious, and a withdrawn young man. On completing his graduation from Prince of Wales College (Now GGM Science College), Jammu, he was commissioned on 14 June 1921, in the J&K Armed Forces. Devoting all his energies to his work, he developed into a towering personality and cultivated all the qualities of a trusted and capable army officer. Rajinder Singh rose to the rank of Brigadier in May 1942. He had been approved for the rank of Major General when he became the Chief of Army Staff (COAS) of the J&K Forces on 25 September 1947. He had taken charge from Major General H.L. Scott. It was a time when the state was in a deep military and political crisis.