This chart shows the competition between India and China's submarine fleet

China and India, the world's two most populous states, share the world's longest contested land border. The two nations also have the dubious distinction of being the largest weapons importers on earth.

Although China and India have attempted to improve relations, the two countries remain locked in a geopolitical struggle for influence. This competition has become especially apparent in Chinese and Indian designs for the Indian Ocean.

Both nations are aggressively seeking to expand their projected maritime power in the region, especially through the use of submarines. The following Reuters chart compares their submarine fleets.

RNGS REUTERS

In terms of both quantity and technological advancement, China's submarine fleet drastically outperforms India's. Beijing has nine nuclear submarines alone compared to India's one nuclear Chakra sub.

The Chakra sub is an Akula-class Russian nuclear attack submarine that India is leasing for ten years, USNI News reports. China's nuclear submarines, on the other hand, are a mixture of attack and ballistic missile vessels that were indigenously built.

Nuclear submarines are far superior to their diesel counterparts. Whereas nuclear submarines can stay submerged for months and are nearly silent, diesel subs are significantly louder and must surface more frequently for oxygen. All of this contributes towards diesel submarines being significantly less effective than nuclear submarines, which have a greater range and are more easy for the enemy to spot.

In response to a lack of effective subs, New Dehli has reached out to Japan on a possible initiative to build submarines in India, The Diplomat reports. This offer is part of a move by India to update its submarine fleet, and New Dehli is also considering acquiring submarines from France, Germany, Russia, and Spain.

Reuters

A Chinese Naval submarine docks at the Ngong Shuen Chau Naval Base in Hong Kong.

India's desire to acquire more submarines is closely related to concerns over China.

Beijing has been steadily investing in port installations in Pakistan, Bangladesh, Sri Lanka, and Myanmar. These ports have allowed for Chinese merchant vessels, in addition to submarines and warships, to have safe harbor throughout the entirety of the Indian Ocean.

China recently raised Indian suspicions by docking submarines at the port of Colombo in nearby Sri Lanka, and there is concern that Beijing is trying to construct a "string of pearls" through the Indian Ocean in order to establish naval and commercial superiority on India's strategic turf.