US pacts with Tokyo and Seoul offer clues on how one with Riyadh might look like

Overcoming animosity

By the time of President Obama, the American focus in Asia had shifted away from the Russian threat to North Korea and China. The US wanted Japan and South Korea to overcome deep historical grievances and work together.

After much diplomatic effort, Biden succeeded in bringing the leaders of Japan and South Korea to Camp David last August for the first trilateral summit.

There, the three leaders agreed to hold an annual trilateral summit, conduct regular trilateral military exercises, and establish a three-way emergency contact system between the leaders. Deterring North Korea is the immediate goal of this alliance, but the trilateral alliance also sends a message to China. 

A similar American approach with Saudi Arabia indicates that Washington will want the treaty to bolster Saudi security and the Middle East region.

Deterring Iran will be the obvious immediate goal, but the Americans will want to build military relations between Israel and Arab states, including Saudi Arabia.

It is easy to imagine that if Biden wins in November, his second administration will push for top-level meetings, likely hosted at first by the Americans.

Defence integration

The American military is already conducting regional training exercises with Gulf states in areas such as maritime security and defence against air and missile attacks.

To increase deterrence against Iran as much as possible, and after signing a defence treaty, Washington would encourage regional training exercises to include Israel, which can bring important capabilities to regional efforts like missile defence and security in the Red Sea.

The US treaties with South Korea and Japan require that US military forces defend Korean and Japanese territories alongside Japanese and South Korean forces.

Because of this, the Americans have taken a strong interest in the quality of their Asian allies' military forces for the past several decades.

The US wants to improve its cooperation with its Korean and Japanese counterparts, so it conducts regular bilateral military exercises to improve joint operations capabilities.

The US has even inputted into national Korean and Japanese debates over defence budgets and military structures, with Washington having urged them both to increase defence spending.

The Americans have also pressed their allies to make military adjustments to integrate American weapons, from F-35 jets to cruise missiles to communications equipment.

Joint commands

The Americans also created a Combined Forces Command with a US commanding general and a South Korean deputy commander. It operationalises the 600,000 American and South Korean forces in South Korea.

In the event of a North Korean attack, this joint American-South Korean command would direct the two countries' militaries to defend South Korea.

The Japanese constitution and its politics impede the establishment of a similar bilateral command centre in Japan. The published guidelines for implementing the US-Japan treaty stress that Japanese forces are primarily responsible for defending Japan.

Instead, the US supports Japanese measures to improve the ability to coordinate Japanese ground, air, and naval operations in a single operation.

The Americans may change and expand their own command structure in Japan to interact daily with the new Japanese joint operations command.

Lessons for Riyadh

The experience of Japan and the Republic of Korea indicates that if a bilateral treaty is signed with Riyadh, Washington will pay closer attention to the Saudi government's military budget and how it spends its defence allocation.

The Pentagon, in the end, will have two goals: first, to be able to win a defence war and thus deter enemies like Iran and second, if there is a war, to win with the minimum amount of American and allied casualties.

An official American commitment to defend Saudi Arabia will give incentives to the Pentagon to insist that Saudi military units and commands be able to work smoothly and quickly with the Americans in a crisis.

Washington will, therefore, insist on much more detailed joint planning. The Pentagon also will not hesitate to speak more frankly and with greater insistence to facilitate the US-Saudi military coordination in a crisis. At the same time, Washington would also want to expand its training and advising mission to Saudi military elements.

Nuclear threats

If Iran directly attempts to develop a nuclear weapon, the American response after the signing of a bilateral security agreement likely would be to establish a permanent consultation group.

In Asia, South Korea and Japan are concerned about North Korea's growing nuclear and missile capabilities. The South Korean president raised this issue directly with President Biden during his April 2023 visit.

The Americans responded with the joint 'Washington Declaration' to try to increase deterrence against the North Korean nuclear threat.

Seoul and Washington pledged to increase joint military exercises and plan to increase the South Korean military's ability to support American military units deploying nuclear weapons.

They also established a bilateral Nuclear Consultative Group that met for the first time in June 2023. Consultation aside, there are still questions about whether the Washington Declaration can deter North Korea indefinitely.

Fair contributions

American involvement in Saudi defence spending would be motivated by the need to show US citizens that their allies are paying their way and not simply relying on the American military (and, therefore, on American tax contributions).

A big difference between US security pacts with Japan and South Korea, on the one hand, and a possible deal with Saudi Arabia, on the other, is the issue of troop deployment.

Washington will not want to deploy a large contingent of American military forces to Saudi Arabia, as it has in Japan and South Korea. There are about 50,000 US troops in Japan, mostly Air Force, Navy, and Marines, and about 28,000 in South Korea, mostly Army.

From the 1970s, when the Japanese and South Korean economies were at the visible peak of their strength, Washington pressed the two countries to pay a substantial portion of the cost of American forces in their countries.

In 2022, the Japanese government agreed to pay Washington $8.6bn for costs associated with the American military presence there.

The US and Japan negotiated a set of specific costs for which Japan would be responsible, including the salaries of 23,000 Japanese workers at US bases, the utilities costs at the bases, and some construction costs.

Similarly, the Republic of Korea agreed to pay around $1bn for specific costs, including utilities and construction.

If a security agreement with Saudi Arabia reaches the US Senate, where two-thirds must approve it, the issue of cost-sharing (or, in American political dialect, "burden sharing") will surely arise.

About 2,700 US troops are now training and advising the Saudi military. At a minimum, there will be a very public discussion of Riyadh's financial obligations, both past and future.

Tougher with Trump

If Donald Trump returns to the Oval Office next year, he will take a tougher line with defence treaty allies, as we saw with NATO and South Korea in particular.

Trump is sceptical of treaties that force the US to defend foreign countries. He also takes pride in extracting more money from allies for burden-sharing.

That seemed to be his sole focus when it came to NATO and South Korea, without regard to other elements of bilateral relationships.

Although Seoul offered concessions to Trump on trade policies, it gained no relief on the burden-sharing negotiations despite the growing threat from North Korea.

Therefore, it is easier to imagine a second Biden administration concluding a defence treaty with Saudi Arabia than a second Trump administration.