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While the Atlantic partnership will always remain important for the United States, it is the United States’ ties with India that will be the “defining partnership” of the twenty-first century. Ties with India are the result of more than two decades of efforts by Indian and American leaders, and they will remain steady despite ups and downs because they rest on an underpinning not only of hard power but of soft power.

India is one of the fastest growing economies in the world today, and American companies aim to benefit from the Indian economic boom. Bilateral trade today stands at over $50 billion and American foreign investment in India is approximately $16 billion. The potential for collaboration in the fields of science and technology between the U.S. and...