The United States spent more than $34 billion to maintain military presences in Japan and South Korea between 2016 and 2019, the Government Accountability Office said in a report released March 17.
The two allies combined provided more than $18 billion in financial support for the U.S. military presence there over that four-year period, GAO said in the report, "Burden Sharing: Benefits and Costs Associated with the U.S. Military Presence in Japan and South Korea."
During his presidency, former President Trump frequently castigated allies such as NATO nations, South Korea and Japan for not paying their "fair share" of the cost to maintain an American military presence abroad. In 2019, for example, the Trump administration asked Tokyo to roughly quadruple the amount it contributed to the costs of maintaining U.S. troops in Japan.
The report on U.S. spending to keep troops in the two countries was required by Congress in the fiscal 2020 defense budget bill. In all, more than 80,000 U.S. troops are deployed to Japan and South Korea. In Japan alone, the U.S. maintains more than 55,000 deployed troops -- the largest forward-deployed U.S. force anywhere in the world.
U.S. forces have been in Japan since the end of World War II, first as an occupying force and then as an ally, and in South Korea since the Korean War erupted seven decades ago.
"We found that U.S. forces help strengthen alliances, promote a free and open Indo-Pacific region, provide quick response to emergencies and are essential for U.S. national security," GAO staff wrote in the report.
In all, the U.S. obligated $20.9 billion in funds to maintain its military presence in Japan over those four years, GAO said. The Air Force spent the most of the four services during that time, $7 billion, to support its forces in Japan, slightly more than the U.S. Marine Corps' $6.8 billion.
In South Korea, the U.S. military obligated $13.4 billion between 2016 and 2019. The Army provided the lion's share of military spending there, accounting for $9.2 billion in obligations largely at Camp Humphreys, with the Air Force's $3.9 billion to support Osan and Kunsan air bases coming in second.
The U.S. price tags incurred in both nations stayed relatively steady all four years, with slight increases in 2018, GAO said.
Japan and South Korea each provided lesser amounts in direct financial support, which included cash payments from the nations' governments and direct financial support for labor, utilities and relocating live-fire training away from populated locations, GAO said. Japan provided $12.6 billion in support and South Korea provided $5.8 billion, GAO said.
Japan's annual contributions increased from nearly $2.8 billion in 2016 to almost $3.5 billion in 2018, before dropping to almost $3.2 billion in 2019, GAO said. And South Korea's contributions fluctuated from $1.2 billion in 2016 to $1.7 billion the next year, before dropping to $1.3 billion in 2018 and then hitting $1.5 billion in 2019.
The two allies also have provided indirect financial support to the U.S. that is harder to quantify, GAO said. That includes foregone rents and revenues on land used by the U.S. military that the host nations otherwise could lease and develop, as well as waived taxes and fees on U.S. forces stationed there.
Nine experts consulted by GAO researchers said that the U.S. sees several benefits to national and regional security from having troops stationed in its closest allies in Asia, including maintaining stability in the region and deterring aggression from adversaries such as China, Russia and North Korea.
However, a few experts cautioned that there are drawbacks to the deterrence mission there, most notably that it makes U.S. troops vulnerable to a potential first strike from an adversary.
The U.S. military presence there also improves Japan’s and South Korea's military capabilities, ability to work together through joint training operations and intelligence sharing, experts agreed, and allows the U.S. to respond quickly to rapidly unfolding emergencies such as natural disasters. Some experts agreed that having U.S. forces in Japan and South Korea supports denuclearization and anti-nuclear proliferation operations, though others were skeptical that U.S. forces are helping nudge North Korea to yield its nuclear weapons.
The experts all agreed that U.S. troops' presence bolsters the alliance with Japan and South Korea, and that the nations are reassured by America's willingness to place its own service members in harm's way. Two experts said the American presence also has helped stabilize the "historically fraught relationship between Japan and South Korea," which included a decades-long colonization of Korea that only ended when Japan lost World War II.
However, the opposition to U.S. troops held by some local residents complicates efforts to maintain the alliances, some experts told GAO. The U.S. military presence might not be politically sustainable in areas such as Japan's Okinawa, that have particularly strong feelings against troops being stationed there, experts said.
And having U.S. troops stationed in Japan and South Korea also contributes to maintaining "a free and open Indo-Pacific," where trade routes and supply lines are kept open for free commerce and a rules-based international order is upheld, experts told GAO.