By Christopher Hernandez-Roy

November 2, 2025

U.S. President Donald Trump announced on October 29th that he had granted South Korea approval to build a nuclear-powered submarine. The President said the decision enables South Korea to replace “the old fashioned, and far less nimble, diesel-powered submarines that they have now,” which Canada is considering purchasing. The sub will be built with U.S. propulsion technology at the Philadelphia shipyard owned by Hanwha Ocean Co., Ltd.

Hanwha, along with German company Thyssen Krupp Marine Systems (TKMS), are the two qualified supplier finalists for the Canadian Patrol Submarine Project (CPSP). Trump’s announcement came just as Prime Minister Mark Carney visited Hanwha’s facilities in Geoje, South Korea, to tour the company’s KSS-III (Batch 2) diesel-electric submarine.

South Korea’s pursuit of nuclear-powered submarines (SSNs) represents a major leap in its defence-industrial and technological maturity. Already recognized for its shipbuilding excellence, South Korea’s entry into nuclear-propulsion development places it among a small group of states with advanced submarine manufacturing capacity. For Canada, which seeks to purchase as many as 12 diesel-electric submarines, this development is highly relevant.

If South Korea demonstrates credible nuclear propulsion know-how, it will likely strengthen its export competitiveness and reinforce Canada’s perception of South Korea as a high-end defence partner. It could also allow for a re-think of the wisdom of purchasing 12 conventionally powered boats under the CPSP and prompt the Canadian government to consider instead a mix of diesel-electrics in the medium-term and conventionally armed, nuclear-powered, SSNs in the longer-term.

Globally, the move toward nuclear-powered submarines is reshaping what navies consider state-of-the-art in underwater endurance, range, and stealth. South Korea’s ambitions could raise expectations about the baseline capability Canada should seek. Canada has 162,000 km of Arctic coastline, the longest in the world. As the Northwest Passage becomes increasingly navigable, it will invite other nations, not all of them, friendly, to want to transit through it.

As I have previously argued, a conventionally armed SSN has been recognized in the past as the best option for Canada’s Arctic. However, it introduces logistical, political and budgetary complexities. Given these challenges, submarines with advanced air-independent propulsion systems combined with lithium-ion batteries, which allow them to stay submerged for extended periods, offer the next-best alternative. Both Hanwha’s KSS-III class submarine and Germany’s TKMS Type 212CD sub have already demonstrated excellence in these systems.

Canada must proceed carefully to ensure any platform decision aligns with national security priorities — especially defence of the Arctic — budgetary realities, and existing NATO alliance commitments.

At the same time, as a middle-power develops its own SSN, the perception of obsolescence associated with diesel-electric designs could grow over the lifetime of the CPSP, especially as more of our adversaries operate SSNs or nuclear armed submarines (SSBNs) in the Arctic.

South Korea’s submarine initiative also has geostrategic resonance. It signals a deepening alignment between Washington and Seoul under the U.S.–ROK alliance and may link indirectly with the AUKUS framework. For Canada, a potential CPSP partnership with South Korea could enhance interoperability within the Indo-Pacific security architecture and strengthen ties beyond traditional NATO partners. As South Korea invests in nuclear-propulsion technology, it will expand its supply-chain sophistication across high-grade metals, a potential opportunity for Canada’s critical minerals sector.

At the same time, Canada must assess sustainability implications and whether a drive to build SSNs would impact South Korea’s ability to deliver diesel-electric submarines. It must also consider the implications of partnering with a non-NATO, non-European country, especially as Prime Minister Carney has discussed building stronger trade and defence ties with Europe, and signed a Security and Defence Partnership with the European Union aiming to participate in ReArm Europe/Readiness 2030, Europe’s rearmament plan put into place in response to Russia’s war of aggression against Ukraine.

In late August, the Prime Minister and German Chancellor Friedrich Merz agreed to enhance collaboration on defence and critical minerals, which could be tied to an eventual submarine deal with Thyssen Krupp Marine Systems.

The technological leap represented by South Korea’s ambitions could raise expectations for range, endurance, and stealth, but at significantly higher cost than a diesel-electric sub, which has likely been the biggest barrier to Canada considering an SSN. Though it is possible a South Korean SSN would be less costly than the U.S. Virginia Class, or the AUKUS-class boats that the UK and Australia will eventually build.

South Korea’s nuclear-submarine ambitions will likely accelerate its technological and industrial competitiveness. For Canada, this creates both a challenge and an opportunity: competition in the global submarine market intensifies, but so do prospects for partnership. If managed strategically, a collaboration could yield mutual benefits—technological exchange, industrial cooperation, and deeper Indo-Pacific engagement.

Yet, Canada must proceed carefully to ensure any platform decision aligns with national security priorities — especially defence of the Arctic — budgetary realities, and existing NATO alliance commitments. Ultimately, South Korea’s move into nuclear propulsion underscores a broader trend: middle powers are seeking greater strategic autonomy through advanced defence technology.

Canada’s CPSP decision should reflect not just capabilities and cost but also technological advancements, industrial opportunities and long-term geopolitical positioning.

Christopher Hernandez-Roy is a Senior Fellow and Deputy Director of the Americas Program at the Center for Strategic and International Studies.