Defense Priorities Defense Priorities
  • Policy Topics
    • Ukraine-Russia
    • NATO
    • China
    • Syria
    • Israel-Iran
  • Research
    • Briefs
    • Explainers
    • Reports
  • Programs
    • Grand Strategy Program
    • Military Analysis Program
    • Asia Program
    • Middle East Program
  • Experts
  • Events
  • Media
  • About
    • Mission & Vision
    • People
    • Jobs
    • Contact
  • Donate
Select Page
Home / Asia / Bridging the divide: the significance of the U.S.-South Korea-Japan trilateral
Asia, Alliances

August 17, 2023

Bridging the divide: the significance of the U.S.-South Korea-Japan trilateral

By Daniel DePetris

The Philippines may be the oldest US treaty ally in Asia, but South Korea and Japan are arguably the closest. The US-South Korea mutual defence treaty will turn 70 years old this October, and both countries have spent the last several months implementing the April 2023 Washington Declaration that reiterates Washington’s extended deterrence commitment to Seoul in the face of North Korea’s growing nuclear and missile capability. Japan, meanwhile, is undergoing its own defence transformation of sorts, planning a doubling of its defence budget over the next five years and boosting the interoperability of their forces with countries from the Philippines to Australia.

The bilateral relationship between South Korea and Japan, however, has always been a one-step forward, two-steps back situation. Imperial Japan’s thirty five-year colonisation of the Korean Peninsula before and during the Second World War, and all of the human rights abuses that went along with it, was the albatross around the relationship’s neck. Japan and South Korea were more than happy to work with the United States, but the United States was considered lucky if it could drag Japan and South Korea into the same room.

South Korea-Japan relations still aren’t rosy, but they are far better off today than they were four or five years ago.

Read at Lowy Institute

Author

Photo of Daniel DePetris

Daniel
DePetris

Fellow

Defense Priorities

More on Asia

pollTaiwan, Asia, China

Expert survey: Will the U.S. defend Taiwan?

By Jennifer Kavanagh

September 15, 2025

ExplainerTaiwan, Asia, China

Will the U.S. go to war over Taiwan?

By Jennifer Kavanagh

September 15, 2025

op-edTaiwan, Asia, China

Here’s how Trump can prevent a war over Taiwan

By Jennifer Kavanagh

September 15, 2025

op-edAsia, China, Diplomacy

India’s thaw in relations with China is nothing to fear

By Lyle Goldstein

September 14, 2025

In the mediaChina, Asia, Military analysis, Naval power

U.S.-China rivalry sparks a submarine arms race

Featuring Jennifer Kavanagh

September 8, 2025

In the mediaAsia, Taiwan

As South Korea’s leader meets with Trump, China looms large

Featuring Jennifer Kavanagh and Dan Caldwell

August 24, 2025

Events on Asia

See All Events
virtualGreat power competition, Balance of power, China, Grand strategy, Middle East

Past Virtual Event: U.S.-China competition and the value of Middle East influence

June 10, 2025
virtualChina, Alliances, Balance of power, Diplomacy, Grand strategy, Russia

Past Virtual Event: China-Russia: Cooperation or a no-limits alliance?

April 3, 2025
virtualAsia, Basing and force posture, Burden sharing, China, Grand strategy

Past Virtual Event: Rethinking U.S. strategy in East Asia: do more bases mean more deterrence?

January 24, 2024

Receive expert foreign policy analysis

Join the hub of realism and restraint

Expert updates and analysis to enhance your understanding of vital U.S. national security issues

Defense Priority Mono Logo

Our mission is to inform citizens, thought leaders, and policymakers of the importance of a strong, dynamic military—used more judiciously to protect America’s narrowly defined national interests—and promote a realistic grand strategy prioritizing restraint, diplomacy, and free trade to ensure U.S. security.

  • About
  • For Media
  • Jobs
  • Donate
  • Privacy Policy
  • Terms and Conditions
  • Contact
© 2025 Defense Priorities All Right Reserved