https://www.bbc.com/news/world-asia-india-45757556
India has signed a deal with Russia to acquire the S-400 air defence missile system, despite the possibility such a move could trigger US sanctions.
Indian Prime Minister Narendra Modi and Russian President Vladimir Putin announced the $5bn (£3.8bn) deal in Delhi on Friday.
The S-400 is one of the most sophisticated surface-to-air defence systems in the world. It has a range of 400km (248 miles) and can shoot down up to 80 targets simultaneously, aiming two missiles at each one.
India's neighbour China also has the same system - the two countries fought a war in 1962 and routinely see skirmishes on their border. So for India it was imperative to boost its defence capabilities - especially in view of a possible two-front conflict, with Pakistan and China.
Rajiv Nayan, defence expert at the Institute for Defence Studies and Analyses think-tank, believes India had to take "a calculated risk".
"India needs to look after its strategic interests. An air defence missile defence system was the need of the hour. The US has said that going ahead with the deal would attract sanctions - but Delhi cannot be seen coming under pressure," he told the BBC.