Defence Minister Singh also led the preparations and planning for war in Kashmir, which had broken out with Pakistani tribesmen and some military officers had incursed into the state with the aim of annexing it into Pakistan.
In September 1948, under the instructions of the Home Minister Vallabhbhai Patel, Baldev Singh and his commanders prepared plans for Operation Polo, a week-long operation that annexed the princely state of Hyderabad into the Indian Union.