The Republic of Korea (ROK) and the United States completed exercise Iron Mace, aimed at exploring ways to counter increased threats from North Korea.
Iron Mace is a tabletop war simulation designed to integrate the ROK’s conventional capabilities with U.S. nuclear assets. The exercise took place in September 2025 at the U.S. Forces Korea headquarters at Camp Humphreys in Pyeongtaek, about 60 kilometers south of Seoul, according to Yonhap News Agency. It was the third such drill, following similar exercises in August 2024 and April 2025.
While the training traditionally has centered on the Joint Chiefs of Staff of both nations, the 2025 iteration included participation of U.S. Indo-Pacific Command (USINDOPACOM), expanding its scale, according to The Chosun Daily newspaper.
“Given the escalation of North Korea’s nuclear threats, we understand that the number of participating units and personnel has significantly increased compared to the first and second exercises,” a ROK Armed Forces spokesperson told The Chosun Daily at the start of the exercise.
Iron Mace took place under joint nuclear deterrence guidelines adopted by the Nuclear Consultative Group (NCG), a bilateral body established by South Korea and the U.S. following a summit between the two countries in April 2023. NCG brings defense officials from both countries together to develop and maintain a credible nuclear deterrence policy and structure and manage threats. “The NCG is a tangible symbol of the ironclad U.S. extended deterrence commitment to the ROK, which is backed by the full range of U.S. capabilities, including nuclear,” the U.S. State Department said in a news release following the group’s fourth meeting is January 2025.
Concurrent to Iron Mace, Japan joined the ROK and the U.S. to conduct the annual multidomain exercise Freedom Edge in international waters east and south of South Korea’s southern island of Jeju, according to Yonhap News Agency. In its third iteration, Freedom Edge incorporated air and maritime training with cyberwarfare and special operations capabilities as the defense forces executed ballistic missile defense; defensive counterair; anti-surface warfare; maritime operations including board, search and seizure; counterpiracy, medical evacuation; and replenishment-at-sea operations, according to a U.S. Navy news release.
“Freedom Edge is a continuing effort among the three nations to make information sharing and interoperability routine, repeatable and real,” said U.S. Air Force Col. Craig Rumble, warfighting exercise branch chief for USINDOPACOM. “Freedom Edge turns policy into procedures, and procedures into muscle memory — so the U.S., Japan, and Republic of Korea can train and improve together.”
Collaboration among the three nations has increased in the face of escalating threats from North Korea, which is increasing the development of its unregulated, unrecognized (Nuclear Non-Proliferation Treaty non-compliant) nuclear arsenal and increasing cooperation with China, Iran and Russia. In June 2025, Japan, the ROK and the U.S. held combined air drills. In August 2025, the three nations collaborated during exercise Ulchi Freedom Shield and joined several other Indo-Pacific countries for integrated exercises, including Pacific Vanguard in Guam.