The Chakra, one of Russia's famed Akula-II (shark in Russian) class submarine, was taken on lease from Moscow in 2012.
Since then, it has protected India's vast maritime frontiers and helped the nation develop its own indigenous undersea strategic nuclear submarines.
Here's all about it.
What are Akula-class submarines?
The Akula was first introduced by the erstwhile Soviet Union in 1984.
Stealth, the most important element for any submarine, was an area the Soviets lacked.
The Akula's arrival stunned the Soviet Union's NATO adversaries as it ended America's undersea superiority.
Like its namesake, the Akula was truly a silent, fast and deadly shark that lurked deep beneath the ocean, seeking its prey.
What is INS Chakra?
The 12,000-tonne INS Chakra is powered by a 190 MW nuclear reactor and can travel at speeds of over 30 knots.
It has a crew of 80 submariners and unlike India's smaller diesel-electric vessels, features a recreation area, a gymnasium, and a sauna.
It is armed with a wide array of advanced sensors, torpedoes, and tactical missiles.
It can reach a depth of 600-meters.
India's journey to commission INS Chakra ::
India first leased a Charlie-class Soviet nuclear-powered submarine from 1988-91.
After the Soviet Union's breakup, India expressed interest in leasing the Nerpa, an incomplete Akula-class submarine lying at Russia's Amur shipyard.
India paid around $1 billion to lease the submarine for a 10-year period, following which the submarine's construction with modern armaments was completed.
The Indian Navy commissioned the Nerpa, rechristened Chakra, in 2012.
What role does INS Chakra play for Indian Navy?
Nuclear attack submarines such as the Chakra were traditionally primarily tasked with hunting nuclear-powered and nuclear-armed ballistic missile submarines.
They can take out other submarines and warships. They also protect and escort friendly ballistic-missile submarines and warships.
Unlike conventionally-powered diesel-electric submarines, their endurance is not hindered by the need for regular refueling, allowing them to operate for months far away from home-ports.
India looking to lease another Akula-II submarine from Russia ::
The Chakra was commissioned before India's first indigenous nuclear-powered ballistic missile submarine, INS Arihant.
The Chakra has been crucial for training Indian submariners who would form the crew of the Arihant and all subsequent indigenous nuclear submarines.
India is also reportedly looking to lease another Akula-class submarine from Russia to compliment the Chakra.
Besides this, India is developing six new indigenous nuclear attack submarines.