There’s a growing intimacy between two of Asia’s big naval powers and it’s causing disquiet among regional watchers and maritime policymakers. Russia and China are growing closer in the nautical realm, much to the chagrin of Indian, American and Southeast Asian analysts who feel that their growing bilateral synergy could impact the balance of power in Asia.

The trigger for the latest bout of anxiety is ‘Joint Sea-2016’— a joint Sino-Russian naval exercise featuring surface ships, submarines, fixed-wing aircraft, ship-borne helicopters and amphibious vessels navies. China has announced that its biggest naval drill with Russia will include the People’s Liberation Army Navy’s (PLA-N’s) Nanhai fleet, and will involve, among other exercises, anti-submarine and amphibious missions.

This is the first time Russian and Chinese naval contingents are meeting for combat drills in the South China Sea (though reportedly not in a contested part of the region), however there’s been visible evidence of a growing synergy in other parts of maritime Eurasia. In August last year, the two navies carried out ‘Joint Sea 2015 II’, a high-end naval exercise in the Sea of Japan, featuring live-firing drills, anti-submarine operations and close-support combat drills. During an earlier exercise in the Mediterranean Sea and Black Sea in May the same year, senior commanders made statements challenging America’s strategic dominance of Eurasia. Russian and Chinese leaders believe that the US is the central destabilising factor in the region’s geopolitics, and is engaged in a systemic containment of Moscow and Beijing. By staging close-combat naval exercises, they hope to warn Washington that its primacy in maritime Asia is at an end.

The prospect of joint amphibious exercises near the South China Sea has alarmed regional watchers. Many fear a repeat of the August 2015 drills, when the Russian and Chinese navies simulated a mock ground assault in which 400 PLA marines landed on an island in Russia’s Far East. Indeed, since May 2015—when China’s Military Strategy white paper announced an expeditionary template of operations—amphibious missions and airborne landings have been a standard feature of China–Russia joint naval exercises.This time, Beijing’s gone a step further and announced an ‘island-seizing’ exercise involving a sizeable contingent of the PLA Marine Corps.

To be sure, China and Russia have their share of political differences. Russia’s had concerns about Chinese encroachments in the Russian Far-East and the loss of Central Asia to China’s growing influence. Following Moscow’s annexation of Crimea, however, President Vladimir Putin’s had to accommodate growing Chinese ambitions in Russia’s zone of influence. To diversify Russia’s energy export markets away from Europe, Putin has acquiesced to an asymmetric relationship with China, by allowing Beijing to extract the greater share of benefits through a ‘special’ ally status.

Moscow is reassured by China’s continuing dependence on Russia for defence technology. Since December 1992, when the two countries signed an agreement on military technology cooperation, China has purchased more defence items from the Russian Federation than from any other country. These include Kilo-class submarines, Su-27 aircraft, Sovremenny-class destroyers, and many varieties of munitions and missiles. Despite a relative reduction in military sales in the past few years, Russia has continued the supply of vital maritime stores and equipment. The growing maritime cooperation is a manifestation of an essentially robust defence relationship.

Even so, the trajectory of recent maritime interactions suggests that the partnership is beginning to outgrow the original template of military cooperation. Not only has the size of participating contingents grown, the quality of exercises has substantially improved. The military relationship has benefited from a huge political investment from Putin, who’s taken a personal interest in nurturing the partnership. Beijing, in search of an ally to counter-balance the US Navy, has been happy to play along.

The nautical synergy also reveals an enduring correlation between geopolitics and maritime strategy. The Sino–Russian maritime relationship seems driven by political motivations and a desire to jointly counter US military pressure. Putin’s statement during the recent G20 summit supporting China’s rejection of the ruling by the Hague tribunal on the South China Sea is clear evidence that the maritime strategy is being driven by regional politics. Notably, many in Moscow are beginning to view Chinese island infrastructure in the South China Sea as protection for Russia against a US attack. It hasn’t surprised anyone that the Russian Navy has co-opted China as a ‘core partner’ in its new maritime doctrine, signaling a desire for greater maritime influence in the Asia–Pacific.

For New Delhi, the picture of Russia and China holding hands at sea isn’t a pretty one. China’s inclusion of Gwadar port in a US$46 billion China-Pakistan Economic Corridor (CPEC), as well as the announcement of the transfer of eight Yuan-class submarines to Pakistan, has already caused heartburn in India. But Indian policymakers also worry about Russia’s warming defence relationship with Pakistan. After waiving its arms embargo on Pakistan in June 2014, Moscow signed a bilateral defence cooperation agreement with Islamabad, even agreeing to sell Mi-35 helicopters to the Pakistan Army. What really has Indian policymakers worried, however, is Russia’s decision to import Klimov RD-93 engines for the JF-17 aircraft it jointly manufactures with China. In addition, a recent report has suggested Russia and Pakistan are slated to hold their first ever joint military drill in the coming months.

With a friendly Pakistan at hand, if the Sino-Russian nautical concord pushes into the Indian Ocean Region—as is being widely anticipated in the wake of India’s logistics agreement with the US—New Delhi knows it may be hard to reverse the shift in the regional balance of maritime power.