Vallabhbhai Patel as Minister for Home and States Affairs had the responsibility of welding the British Indian provinces and the princely states into a united India.
By far the most significant factor that led to the princes' decision to accede to India was the policy of the Congress and, in particular, of the two key figures in the States Department, Sardar Vallabhbhai Patel and V. P. Menon. The Congress' stated position was that the princely states were not sovereign entities, and as such could not opt to be independent notwithstanding the end of paramountcy. The princely states, it declared, must therefore accede to either India or Pakistan. In July 1946, Nehru pointedly observed that no princely state could prevail militarily against the army of independent India. In January 1947, he said that independent India would not accept the Divine Right of Kings, and in May 1947, he declared that any princely state which refused to join the Constituent Assembly would be treated as an enemy state. Other Congress leaders, such as C. Rajagopalachari, argued that as paramountcy "came into being as a fact and not by agreement", it would necessarily pass to the government of independent India, as the successors of the British.
Patel and Menon, who were charged with the actual job of negotiating with the princes, took a more conciliatory approach than Nehru. The official policy statement of the Government of India made by Patel on 5 July 1947 made no threats. Instead, it emphasised the unity of India and the common interests of the princes and independent India, reassured them about the Congress' intentions, and invited them to join independent India "to make laws sitting together as friends than to make treaties as aliens". He reiterated that the States Department would not attempt to establish a relationship of domination over the princely states. Unlike the Political Department of the British Government, it would not be an instrument of paramountcy, but a medium whereby business could be conducted between the states and India as equals.
In discussions, Lord Mountbatten reinforced the statements of Patel and Menon by emphasising that the documents gave the princes all the "practical independence" they needed. Mountbatten, Patel and Menon also sought to give princes the impression that if they did not accept the terms put to them then, they would subsequently have to accede on substantially less favourable terms. The Standstill Agreement was also used as a negotiating tool, as the States Department categorically ruled out signing a Standstill Agreement with princely states that did not sign an Instrument of Accession.
Help from British leader(s)
A few British leaders, particularly Lord Mountbatten, the last British viceroy in India, were also uncomfortable with breaking links between independent India and the princely states. The development of trade, commerce and communications during the 19th and 20th centuries had bound the princely states to British India through a complex network of interests. Agreements relating to railways, customs, irrigation, the use of ports, and other similar agreements would disappear, posing a serious threat to the economic life of the subcontinent. Mountbatten was also persuaded by the argument of Indian leaders such as V. P. Menon that the integration of the princely states into independent India would to some extent assuage the wounds of partition. The result was that Mountbatten personally favoured and worked towards the accession of princely states to India following the transfer of power, as proposed by the Congress.
As a relative of the British Emperor, he was trusted by most of the princes and was a personal friend of many. The princes also believed that he would be in a position to ensure the independent India adhered to any terms that might be agreed upon, because Jawaharlal Nehru and Patel had asked him to become the first Governor General of the Dominion of India.
Mountbatten used his influence with the princes to push them towards accession. He declared that the British Government would not grant dominion status to any of the princely states, nor would it accept them into the British Commonwealth, which meant that the states would sever all connections with the British crown unless they joined either India or Pakistan. He pointed out that the Indian subcontinent was one economic entity, and that the states would suffer most if the link were broken. He also pointed to the difficulties that princes would face maintaining order in the face of threats such as the rise of communal violence and communist movements.
Mountbatten stressed that he would act as the trustee of the princes' commitment, as he would be serving as India's head of state well into 1948. He engaged in a personal dialogue with reluctant princes, such as the Nawab of Bhopal, who he asked through a confidential letter to sign the Instrument of Accession making Bhopal part of India, which Mountbatten would keep locked up in his safe. It would be handed to the States Department on 15 August only if the Nawab did not change his mind before then, which he was free to do. The Nawab agreed, and did not renege over the deal.
At the time, several princes complained that they were being betrayed by Britain, who they regarded as an ally, and Sir Conrad Corfield resigned his position as head of the Political Department in protest at Mountbatten's policies. Mountbatten's policies were also criticised by the opposition Conservative Party. Winston Churchill compared the language used by the Indian government with that used by Adolf Hitler before the invasion of Austria.