At the time of Partition in 1947, the princely states of India, who in principle had self-government within their own territories, were subject to subsidiary alliances with the British, giving them control of their external relations.
One major exception was that of the wealthiest and most powerful principality, Hyderabad, where the Nizam, Mir Osman Ali Khan, Asaf Jah VII, a Muslim ruler who presided over a largely Hindu population, chose independence and hoped to maintain this with an irregular army.
[5]: 224 Fearing the establishment of a Communist state in Hyderabad by the rebels[6][7] and the rise of Muslim nationalist Razakar militas, India defeated the Razakars [8] and took the state in September 1948 following a crippling economic blockade.
[9] [10] Subsequently, the Nizam signed an instrument of accession, joining India.
[11] The operation led to massive violence on communal lines, at times perpetrated by the Indian Army.