India's planned purchase of 126 fighters from France's Dassault marks the latest stage in a huge military procurement cycle that has turned the world's largest democracy into its biggest arms importer.

The final Dassault contract is expected to be worth $12 billion and India is preparing further big ticket purchases over the coming years, including of helicopters and artillery.

In a report to be published next week, Jane's Defence Weekly forecasts that India's aggregate defence procurement spending between 2011 and 2015 will top $100 billion.

What is less clear -- and the subject of some heated debate -- is why New Delhi is so hungry for costly modern weaponry and where the country's strategic priorities lie.

Some argue that India is simply playing catch-up and using its growing economic wealth to effect a pragmatic, and long overdue, overhaul of a military arsenal still loaded with near-obsolete, Soviet-era hardware.

But others sense a more combative impulse, driven by the military modernisation efforts of its rivals and neighbours Pakistan and China, as well as the need to secure energy resources and supply lines outside its borders.

In testimony Tuesday to a Senate Select Committee, the director of US national intelligence, James Clapper, said India was increasingly concerned about China's posture on their disputed border and the wider South Asia region.

"The Indian military is strengthening its forces in preparation to fight a limited conflict along the disputed border, and is working to balance Chinese power projection in the Indian Ocean," Clapper said.

In order to secure the modern weaponry it needs to buttress its defence imperatives, India has little choice but to spend big in the global arms market.

Its long-stated ambition of sourcing 70 percent of defence equipment from the home market has been hampered by weak domestic production -- the result of the stifling impact of excessive bureaucracy.

Consequently, statistics from the Ministry of Defence show that India still imports 70 percent of its defence hardware.

"Where India has had some success is in joint ventures, and building foreign equipment under license," said James Hardy, Asia Pacific analyst at Jane's -- a respected industry publication.

"The licensed production route seems to be working and at this point in India's development is a good way of overcoming the bureaucratic challenges of indigenous production."

The proposed contract with Dassault envisages the purchase of 18 Rafale aircraft, with the remaining 108 to be built in India.

India's need for a multi-combat fighter is, in part, based on its geographical size which spans several operational theatres with wildly varying topographies.

"The aircraft they have just get worn out," said Hardy. "They want aircraft that can fly, land and take off anywhere from the Himalayas to the deserts of Rajasthan."

While the Indian Army has traditionally taken the lion's share of the national procurement budget, the focus has begun to shift in recent years toward the air force and navy.

In December, Russia handed over a nuclear-powered attack submarine to India on a 10-year lease -- a deal greeted with alarm and anger by Pakistan.

The Akula II class craft is the first nuclear-powered submarine to be operated by India since it decommissioned its last Soviet-built vessel in 1991.

India is currently completing the development of its own Arihant-class nuclear-powered submarine and the Russian delivery is expected to help crews train for the domestic vessel's introduction into service next year.

India is particularly keen to strengthen its maritime capabilities, given China's pursuit of a powerful "blue water" navy which Delhi sees as a threat to key shipping routes in the Indian Ocean and Indian energy assets in the South China Sea.

But many Indian observers reject suggestions that India is even thinking of getting into an arms race with China.

"The Chinese have a huge, huge lead. They are in a different league," said strategic analyst Uday Bhaskar.

"The gap in conventional terms and WMD (weapons of mass destruction) is so wide in China's favour, that it's just not valid to say India is trying to catch up or seek any kind of equivalence.

"India is simply seeking what it sees as a level of self-sufficiency, and is being constrained by its modest outlay and a decision-making process that drives everyone up the wall. That's why we top of the list of arms-importing nations," Bhaskar said.

China, meanwhile, seems content to gently mock what the Communist Party mouthpiece, the People's Daily, in December described as the "persecution mania" driving India's military modernisation.