So, now that I've discussed China and Japan, let me deal with the third major power in the Asian balance-of-power system--India. India has features of three of the great powers of the classical European 19th-20th century system. India today is a country divided between a backward, rural agrarian economy and a modern urban economy based on industry, services, and high-tech. In this it resembles China, but it is not as far along as China began her economic liberalization a full decade before India did. India thus resembles in this aspect Russia in the late 19th and early 20th century say from 1890 to 1917. But unlike Tsarist Russia, India is a democracy and a mature one at that--thus resembling the French Third Republic in this aspect. But in her difficult geopolitical position between Pakistan and China, both on her northern borders, India resembles Germany from 1870 to 1945 and Poland from 1919 to 1939.
India's rulers did not immediately appreciate her difficult geopolitical position after independence. India was one of three originators of the non-aligned movement along with Tito's Yugoslavia and Nasser's Egypt. It was only after China both surprised and humiliated India in the border war of October 1962 that Prime Minister Jawaharlal Nehru and his ministers woke up to their predicament. This was followed by border clashes with Pakistan in the Rann of Kutch in April 1965 followed by a full-scale war later that year. So India's leaders found themselves between the American-supported Pakistan to its northwest and China, an aspiring great power in Asia that went nuclear in 1964, to its northeast. Under Nehru's successor and daughter Prime Minister Indira Gandhi (no relation to the Mahatma), India in reality gave up her non-aligned status and became a client of the Soviet Union. In 1971 Moscow and New Delhi signed a friendship treaty--a standard sign of a Soviet client. This gave India an assured supply of modern arms like MiG fighters, Tupolev bombers, Sukhoi attack planes, and T-55 and T-62 main battle tanks. India also continued to buy some weapons from Britain such as Centurion tanks, ships, and other military supplies. Moscow also supplied India with nuclear deterrence against Beijing. For a lengthier explanation of India's policy in 1971 see this book review.
But like Charles de Gaulle of France, Gandhi was not overly trusting of Moscow and so she decided to develop India's own nuclear deterrent with the use of Western-trained Indian scientists. In 1974 India exploded its own "peaceful nuclear explosion"--named as if its purpose was to excavate a large crater for building a harbor etc. rather than in order to develop a deterrent capability. For two decades India did little else with its nuclear deterrent. India had helped to dismember Pakistan in December 1971 by fighting a holding armor battle in West Pakistan while invading East Pakistan in order to establish the new state of Bangladesh in the place of Pakistan's eastern portion. This was much like what Germany did in 1914 against France and Russia, but against a much weaker opponent. One can imagine that like the German general staff under Field Marshal von Schlieffen, the Indian general staff had worked out its plans ahead of time. Since 1971 India and Pakistan have fought only one more war--in 1999--which consisted mainly of artillery duels and an Indian counterinsurgency campaign against Pakistani subversion in Kashmir.
In May 1998 India conducted a series of nuclear tests to which Pakistan responded with its own series of nuclear tests. As a result Washington sanctioned both countries but eventually lifted the economic sanctions imposed upon India. In August 1999 New Delhi announced that its nuclear weapons were only for deterrent purposes and would not be used before India was subject to a nuclear attack from another nuclear power (read China or Pakistan). While its nuclear force initially consisted mainly of short-range and tactical nuclear weapons deployed near the border with Pakistan, India has continued to develop delivery systems that had ranges to hit targets in China. But Indian development of SLBMs based on nuclear-powered submarines is definitely aimed at China. Go here for a very good slideshow on India's nuclear deterrent capability, and here for an article on her latest ballistic-missile submarine..
Since the end of the Cold War New Delhi has normalized political relations with Washington so that the two are no longer rivals but they are still not quite allies. If the rivalry with China intensifies expect India to increase its military ties with other regional powers such as Japan and Vietnam as well as with Washington. India since independence in 1947 has relied upon a three-pronged trident policy of dealing with her geopolitical position: a robust defense force consisting of a large army and a capable navy as well as an air force; an alliance with the Soviet Union; and an internal nuclear capability. The only thing that is likely to change in the near future is the identity and number of her political and military allies.