- In his first term, Donald Trump ramped up military actions to counter China in the South China Sea.
- Four years later, China has grown more confrontational, leaving less margin for error.
- Tensions are so high that a skirmish could escalate into a regional war, one analyst told BI.
As President-elect Donald Trump prepares to return to office, one of his biggest challenges could be an issue that hardly came up on the campaign trail.
The South China Sea — contested waters that China says are its own and the US says belong to no single nation — has only grown as a risk factor in the years Trump was out of government.
During his first term, Trump's administration took a hard line against China, stepping up its patrols and exercises in the region, and rejecting Chinese territorial claims.
Since then, China has expanded its presence in the region, growing more willing to confront other countries there, including the Philippines, an ally the US is treaty-bound to defend.
"The margin for error has shrunk since 2016-2020," said Hunter Marston, an Asia-Pacific researcher at the Australian National University.
"It would now take less of a spark for a skirmish or collision to trigger a conflict involving all parties," he said.
A vital ally
Trump hasn't said how he would handle the region in his second term as president.
South China Sea observers expect continuity with the Biden administration, which tried to ramp up diplomatic efforts and strengthen US alliances and security partnerships.
Gregory Poling, director of Southeast Asia Program at the Center for Strategic and International Studies, said that Trump "introduces a level of personal unpredictability compared to Biden."
"But there is no reason to expect any major changes to US policies on this front."
A delicate balance to strike
Trump, like President Joe Biden before him, has a delicate balance to navigate.
Recent months have seen clashes between Chinese and Filipino coast guard vessels, including one where swords and knives were brandished.
Under a treaty from 1951, the US is obliged to aid the Philippines against armed attack — something China has avoided through so-called gray-zone operations that are not technically "armed."
The Filipino secretary of national defense told CBS News' "60 Minutes" in September that there were ongoing discussions about exactly what would prompt US intervention.
Though Trump hasn't outlined a specific South China Sea plan, he could pursue his broader foreign policy mantra of "peace through strength."
That brings its own risks.
"Unrestrained US militarization is precisely what drives Beijing's insecurity and will continue to exacerbate tensions in the South China Sea," Marston said.
An alliance at stake
Sari Arho Havrén, an associate fellow at the UK's Royal United Services Institute specializing in China, said Trump would need to decide how much to commit to the region.
"To be globally influential, the US needs its allies," she said.
Trump has often adopted a skeptical posture toward alliances he deemed unfair to the US — including its roles in helping the defense of Europe, its support for Ukraine, and its military commitments in South Korea.
Zeno Leoni, a lecturer at King's College London's Defense Studies Department, believes US economic interests in the South China Sea make the region an exception.
A yearlong conflict in East Asia, which covers the South China Sea, could result in a 5-10% loss of US GDP, according to a 2016 research report by the Rand Corporation, a prominent think tank.
Leoni believes the Trump administration will try to achieve balance.
"Both Trump's and Biden's National Security Strategy prioritized tackling the rise of China, and this is unlikely to change in the context of a more isolationist foreign policy," he said.