Here's What You Need to Know: Beijing has ramped up talk of being able to blockade India with nuclear submarines.

Back in 2015, the Indian-based news outlet, NDTV, cited unnamed Indian naval sources as saying that India’s Navy is worried by China’s increasingly frequent submarine deployments in the Indian Ocean.

In September 2013, China confirmed for the first time that a nuclear attack submarine would transit the Indian Ocean on its way to carry out the international anti-piracy mission in the Gulf of Aden. This was followed by submarines docking in the Chinese-funded Colombo port of Sri Lanka twice last year.

The first docking, back in September 2014, was a Song-class diesel-electric attack submarine. However, seven weeks later a Type 091 Han-class nuclear-powered submarine surfaced in Sri Lanka. Around the same time, China reportedly informed India that a Type-093 Shang-class nuclear-powered attack submarine would begin patrolling in the Indian Ocean.

It is these nuclear-powered submarines that are particularly worrisome to the Indian Navy. As NDTV reports, “the deployment of the relatively advanced Shang Class nuclear fast attack boat, [is] a significant cause of concern at Naval Headquarters.”

Both India and China rely heavily on sea-borne commerce that transits the Indian Ocean on its way to Beijing and Delhi. For example, trade represents nearly 55 percent of India’s GDP, most of which is carried by sea. China is even more reliant on trade, which in recent years has comprised about 60 percent of China’s GDP. Roughly 85 percent of China’s trade is seaborne.

As such, both countries are highly concerned about their vulnerability to potential blockades, which submarines would be crucial in enforcing.

Indeed, just this week Want China Times noted that the Sina Military Network, a Beijing-based defense website, recently speculated that China could blockade India’s eastern and western coastlines with just ten attack submarines. Specifically, “the Sina Military Network concluded that the PLA's three Type 091 Han-class, four Type 093 Shang-class and two Type 095 attack submarines” could blockade these coasts, according to Want China Times (Interestingly, Sina Military Network made note of the NDTV article cited above).

Sina Military Network went on to say that just six submarines would be necessary to render India’s three military naval bases—located at Mumbai, Karwar and Visakhapatnam—moot.

China operates a massive undersea fleet, with the U.S. Navy confirming in February of this year that the PLA Navy now boasts more attack submarines than it currently possesses.

“Their submarine force has grown over a tremendous rate. They now have more diesel and nuclear attack submarines than we have so they’ve passed us in total quantity — but in quality they are still not there,” Vice Adm. Joseph Mulloy, deputy chief of Naval operations, integration of capabilities and resources, told Congress.

As Mulloy’s statement indicates, China also has one of the fastest growing undersea fleets in the world. In April 2015, for example, China Daily reported that China was getting set to launch three of its most advanced 093G-Type nuclear-powered attack submarines.

China Daily said of the fourth-generation attack submarines:

“The Type-093G is reported to be an upgraded version of Type-093, China’s second-generation nuclear-powered attack submarine, which entered active service several years ago. With a teardrop hull, the submarine is longer than its predecessor and has a vertical launching system.”

The Type-093s are expected to be equipped with China’s new YJ-18 supersonic anti-ship missile, according to China Daily.

The same article reported that China “has about four nuclear-powered Type-094 ballistic missile submarines, up to six Type-093 nuclear-powered attack submarines and about three old Type-091 nuclear-powered attack submarines.”

Zachary Keck is former managing editor of The National Interest. You can find him on Twitter: @ZacharyKeck.

This article first appeared in 2015.

Image: Reuters