In June 2019, the Department of Defense published a new Indo-Pacific strategy. Outlining goals for pursuing preparedness, partnerships, and the promotion of a networked region, the United States made clear its intentions to guarantee open sea lanes and stability in a part of the world that quickly has become a hub of geopolitics and economics.1
A potential obstacle to a free and open Indo-Pacific, however, is the militarization of the maritime environment, especially the undersea domain. No longer content to let the United States handle maritime security and increasingly wary of Chinese activities in the region, more Indo-Pacific countries are taking maritime security into their own hands.2 A direct consequence is soaring military spending. Between 2008 and 2018, defense budgets in Asia expanded by more than 52 percent.3
Moreover, a growing number of countries now operate submarines in the Indo-Pacific. China boasts an estimated 60 submarines, with plans to expand and upgrade its fleet of both diesel and nuclear platforms.4 Thailand and Bangladesh recently entered agreements with China to buy submarines, and the Philippines reportedly is exploring options.5 Other existing submarine powers, such as Australia, Vietnam, Singapore, India, Indonesia, South Korea, and Japan, are either expanding or upgrading their fleets. At this rate, there will be an estimated 250 submarines operating in Asia by 2030.6 With the exception of China, the majority of Indo-Pacific countries are unlikely to become threats to U.S. undersea dominance, and, indeed, many of the submarine powers in the region are U.S. allies. Instead, the most immediate threat presented by this trend of submarine proliferation is the potential consequences for regional stability and maritime security.
Challenges of Submarine Proliferation
Submarines require well-trained crews and an extensive maintenance infrastructure. Not all countries may be able to provide the resources and expertise required for safe operations, and with the region’s already busy seas, more submarines makes the room for error even smaller. Navies in the Indo-Pacific are building up their submarine forces, but it remains to be seen how safely they will be able to deploy them.
Military commanders operating in a crisis environment also face limited access to information, high stress, and time pressure, and these issues are compounded by the nature of submarine operations. Making the right decision will depend on submarine commanders’ training and circumstances—one brash move could lead to a swift escalation of tensions. Consider, for example, the Cuban Missile Crisis, when a submarine brought the world to the brink of nuclear war.
In the heat of the crisis, the Soviets sent four submarines equipped with nuclear torpedoes to Cuba. U.S. anti-submarine forces’ orders were to use only harmless practice depth charges, to attempt to get the submarines to surface. A notice of these instructions also was sent through the U.S. embassy in Moscow to the Soviet government. However, because of faulty communication, a persistent challenge for all submarine forces, the Soviet submarine captains did not receive these signaling procedures. When bombarded with practice depth charges, the captain of the B-59 perceived it to be a potential act of war, and he ordered the preparation of a nuclear torpedo to respond to what he thought was a U.S. attack. Fortunately, he was talked down by another officer on board.7
Many navies today will face similar challenges in training crews and maintaining adequate command and control in the fog of war. Given how recently many Indo-Pacific countries acquired submarines, the growing number of boats could further destabilize the region’s security environment.
Compounding the risk, the Indo-Pacific is a particularly challenging region, rife with potential causes for conflict—including the ongoing South China Sea disputes, cross-strait relations, and tensions on the Korean Peninsula. While submarine proliferation there may not be a direct threat to the United States, it could have second-order effects that could undermine U.S. interests in the region.An accidental escalation of a crisis could pull the United States in through its mutual defense treaties or disrupt key shipping lanes vital to the U.S. economy.
Building a Peaceful Undersea Environment
The United States is uniquely suited to lead and to help mitigate the potential risks of submarine proliferation. Its diplomatic influence, competency in undersea warfare, and extensive security networks can advance a safer Indo-Pacific through preparedness, partnerships, and the promotion of a networked region.
To start, the United States can expand existing lines of communication and dialogues in times of peace to ensure there is proper signaling during a crisis. Already, the United States and other Indo-Pacific powers participate in important events such as the Shangri-La Dialogue and Asia-Pacific Roundtable. These forums are excellent opportunities to discuss the implications of submarine proliferation and how it might affect conflict escalation.
Building on these initiatives, the United States could support Singapore’s initiative to establish a code of conduct for submarines.8 Similar to the Code for Unplanned Encounters at Sea, a parallel Code for Unplanned Undersea Encounters, although nonbinding, could provide guidance to new submarine powers and reduce the potential for accidents.9
Second, the United States should look at expanding the triennial Pacific Reach exercise to as many Indo-Pacific countries as possible. Focused on coordinating submarine rescue operations, this exercise is an excellent opportunity for increased regional cooperation and confidence building and could help reinforce norms of communication in the open ocean. And if a crisis should arise, the United States should use its diplomatic heft to increase communications between disputing actors and prevent escalation.
Finally, the United States should tap into its alliance networks, not only to encourage the safe operation of other navies’ boats, but also to amplify its undersea warfare capabilities. In an era of great power competition, the United States should seize every opportunity to hone its capabilities in the undersea domain. Regular antisubmarine warfare (ASW) exercises, such as during Malabar with India and Japan, are a great start. The United States should look at inviting other Indo-Pacific countries, such as Indonesia, the Philippines, and Vietnam, to join ASW exercises. International exercises can help promulgate best practices and promote safer behaviors under the seas.
Increased ASW intelligence sharing with allies also could alleviate confusion in the undersea environment and provide a more complete picture of underwater activities in the region, especially with regard to Chinese undersea warfare practices. And for the closest U.S. allies, the United States could consider more personnel exchanges to help train each others’ sailors.
Together, these efforts can improve the capability of allies in undersea warfare and the safety of all involved. While submarine proliferation is a growing problem, the United States has an opportunity to take the lead in creating a more stable Indo-Pacific beneath the waves.
1. Department of Defense, Indo-Pacific Strategy Report: Preparedness, Partnerships, and Promoting a Networked Region, 1 June 2019.
2. “Asia Loses Confidence in US Leadership,” Asia Sentinel, 4 June 2019.
3. David Pierson, “Military Spending Is Soaring in the Asia-Pacific Region. Here’s Why,” Los Angeles Times, 7 June 2019.
4. “China Submarine Capabilities,” Nuclear Threat Initiative, 9 October 2019.
5. Koh Swee Lean Collin, “Submarines: A Silent Risk in Asia’s Waters,” The Strait Times, 8 June 2017; and Mike Yeo, “Thai Submarine Purchase Hits Rough Seas, Defense News, 28 August 2020.
6. Collin, “Submarines: A Silent Risk.”
7. Svetlana V. Savranskaya, “New Sources on the Role of Soviet Submarines in the Cuban Missile Crisis,” Journal of Strategic Studies 28, no. 2 (2005): 249–51.
8. David Boey, “Singapore Navy Suggests Code of Conduct for Submarines,” The Strait Times, 30 June 2016.
9. Zhenhua Lu, “The Pacific Is Filling Up with Submarines, Raising Warnings about an Underwater Code of Conduct,” Business Insider, 27 March 2019.