The Operation Polo was associa- ted with the annexation of which one among the following Princely States into Indian Union ?

Operation Polo was the military code name for the annexation of the princely state of Hyderabad into the Indian Union in September 1948 [5]. Following India's independence, the Nizam of Hyderabad, Mir Osman Ali Khan, initially sought a sovereign status and signed a Standstill Agreement with India in November 1947 [1]. However, the rise of the Razakkars (a paramilitary militia) and widespread internal violence led the Indian government to intervene [3]. Described officially as a "police action" to restore law and order, the military operation lasted five days (September 13–18, 1948) and resulted in the successful integration of Hyderabad into India [5]. In contrast, Junagarh was integrated following a plebiscite [4], Kashmir through an Instrument of Accession signed by Maharaja Hari Singh in October 1947, and Travancore through diplomatic pressure and accession.

Sources

1. [1] Rajiv Ahir. A Brief History of Modern India (2019 ed.). SPECTRUM. > Chapter 34: The Indian States > Plebiscite and Army Action > p. 608
2. [5] https://en.wikipedia.org/wiki/Annexation_of_Hyderabad
3. [3] Rajiv Ahir. A Brief History of Modern India (2019 ed.). SPECTRUM. > Chapter 38: Developments under Nehru’s Leadership (1947-64) > Kashmir Issue > p. 649
4. [4] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 16: India–Political Aspects > The Kashmir Problem > p. 38