Explanation:

Instrument of Accession was a legal document first introduced by the Government of India Act 1935 and used in 1947 to enable each of the rulers of the princely states under British paramountcy to join one of the new dominions of India or Pakistan created by the Partition of British India. The instruments of accession executed by the rulers, provided for the accession of states to the Dominion of India (or Pakistan) on three subjects, namely, defence, external affairs and communications.