5 days ago
US Nuclear Guarantees Face New Doubts in Japan, Korea
The United States promises to help protect Japan and South Korea if they face a major attack.
This promise includes the possibility that the United States could use its nuclear weapons to discourage an enemy.
Some people now worry that this protection may not always be dependable.
They point to China’s growing military strength, North Korea’s nuclear weapons and missiles, and unclear US policies.
South Korea is discussing whether it should get more control over nuclear technology or host US tactical nuclear weapons.
Japan has advanced nuclear technology but most of its people oppose owning nuclear weapons.
Some Japanese officials want to discuss whether allied nuclear weapons should be allowed in Japan.
Both countries are trying to decide how much they can rely on the United States for their future security.
The United States provides bilateral security guarantees and an extended nuclear deterrent to Japan and South Korea.
Growing Chinese military power, North Korean missile activity and uncertainty over US commitments are prompting reassessments.
South Korea is considering options including renewed US tactical nuclear deployments or developing greater nuclear capability.
A 2025 Trump-Lee summit included discussions of South Korea’s right to reprocess spent nuclear fuel.
Japan remains publicly opposed to nuclear weapons, while officials debate revising its non-nuclear principles and allowing allied deployments.
- Who
- The United States, Japan, the Republic of Korea, China, North Korea and their leaders and security officials.
- What
- Japan and South Korea are reassessing the dependability of the US extended nuclear deterrent and considering alternative security options.
- Where
- The Indo-Pacific, especially Japan and the Korean Peninsula.
- When
- The reassessment is occurring amid developments over the last decade; the article also cites the April 2023 Washington Declaration and an August 2025 Trump-Lee summit.
- Why
- Concerns include China’s military expansion, North Korea’s nuclear and missile capabilities, uncertainty about US commitments and tensions affecting existing alliances.
Supporters of stronger independent deterrence
Supporters of existing non-nuclear arrangements
South Korea’s nuclear options
Supporters of stronger independent deterrence
South Korea should consider renewed deployment of US tactical nuclear weapons or gradually strengthen its ability to develop nuclear weapons because North Korea is unlikely to denuclearise and China is also nuclear-armed.
Supporters of existing non-nuclear arrangements
South Korea remains covered by the US nuclear umbrella and has instead pursued greater consultation through arrangements such as the Washington Declaration.
Japan’s nuclear policy
Supporters of stronger independent deterrence
Supporters of a tougher policy argue that Japan should discuss nuclear deterrence and potentially revise the Three Non-nuclear Principles to permit allied nuclear deployments.
Supporters of existing non-nuclear arrangements
Japan’s postwar principles prohibit possessing, producing or introducing nuclear weapons, and public opinion remains opposed to Japan acquiring its own arsenal.
Reliance on the United States
Supporters of stronger independent deterrence
Sceptics argue that US actions and ambiguous commitments, combined with China’s military growth, raise doubts about whether Washington would respond decisively in a crisis.
Supporters of existing non-nuclear arrangements
The United States continues to maintain formal bilateral defence agreements and extended nuclear deterrence commitments with Japan and South Korea.
Key facts
- US personnel in South Korea
- About 28,000 US defence personnel are deployed in South Korea.
- South Korea’s nuclear position
- A recent poll cited in the article found 76.2% support for South Korea acquiring nuclear weapons.
- Japan’s nuclear position
- The article says 56.7% of supporters of the Sanae Takaichi government oppose acquiring nuclear weapons.
- Japan’s nuclear capability
- Japan is described as having mastery of the complete nuclear fuel cycle and potentially being able to build a functional arsenal in three to five years without a nuclear test.
- South Korean spent fuel
- South Korea stores more than 500,000 bundles of spent fuel, occupying 98.1% of its total storage capacity.
- Washington Declaration
- The April 29, 2023 declaration by Joe Biden and Yoon Suk Yeol established a bilateral Nuclear Consultative Group.
- Japan-Taiwan distance
- The distance between Taiwan and Japan’s Okinawa island is stated as approximately 790 kilometres.
Sources
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