The year 2024 will see key elections in a number of large and geopolitically significant polities such as Russia, India, Indonesia, South Korea and Taiwan, but the U.S. presidential race will have by far the biggest impact on Japanese policymakers.

If Donald Trump, the outspoken former U.S. president who had little interest in prioritizing security alliances during his tenure, returns to the White House, Japan could be forced to deal with a militarily emboldened China and North Korea, with reduced U.S. engagement in the region, experts in diplomacy and security believe.

Against the backdrop of a potential weakening of the U.S. role in containing China's military rise and a buoyed North Korea operating with fewer inhibitions in a multipolar world order, Tokyo will face greater pressure to demonstrate the benefits of Japan-U.S. security ties, while understanding it is more important than ever to bolster its defense capabilities, the experts added.

Former U.S. President Donald Trump, one of the Republican presidential nominee candidates for the 2024 election, attends a campaign event in Iowa on Dec. 13, 2023. (Getty/Kyodo)

Prospects are growing that incumbent Democrat President Joe Biden and Trump will face off at the Nov. 5 election in a rematch of the 2020 race, with the latter maintaining a comfortable lead in media polls for the Republican primary vote.

"If Mr. Trump becomes the president, he would return to his 'America first' policies and pursue them more vigorously by forming his administration only with his supporters," said Tetsuo Kotani, an international security expert at Meikai University.

In a departure from Trump's first administration which ran from 2017 to 2021 and had "decent" people who saw a need to strengthen the Japan-U.S. alliance and U.S. defense posture in the Indo-Pacific region, Kotani believes "we would see weakening U.S. commitment to defending" Japan in a second term.

During the four-year term, Trump stuck to his criticism of the alliance with Tokyo as unfair and one-sided, since their bilateral security treaty promises U.S. support if Japan is attacked but does not oblige Japan's Self-Defense Forces to reciprocate.

Threatening to end alliances, the businessman-turned-president called on Washington's allies, including South Korea and NATO members, to pay their "fair share," namely, more money for hosting the U.S. military.

In recent years, Japan has beefed up its alliance with the United States and security ties with like-minded countries like Australia and South Korea to enhance deterrence against Beijing's provocative military activities in the East China Sea, including near Taiwan.

A contingency involving the self-governed democratic island is a particularly concerning prospect for Japan, given the proximity of its southwestern islands to the territory, including the Tokyo-controlled, Beijing-claimed Senkaku Islands.

Biden has spoken of his nation's commitment to defending Taiwan, seen by Communist-led China as a breakaway province to be brought into its fold, but Washington officially maintains a policy of "strategic ambiguity" that keeps its options open in the event of a Chinese attack.

Conversely, Trump has been evasive when questioned on whether the United States would get involved militarily in a Taiwan contingency.

Kotani pointed out the possibility that Trump could even be willing to use Taiwan as a bargaining chip in a "deal" with China, reflecting how little he values the island's "strategic importance."

"For example, he may make a proposal that the United States commit to never interfering in the Taiwan issue if China makes some concessions on disputes related to trade or technology," he said.

Given North Korea's missile and nuclear programs and military collaboration with China and Russia during Moscow's invasion of Ukraine, Kotani said Japan is now in one of the world's most challenging security environments, making the alliance with the United States all the more important.

"But it is not a factor to be considered at all in Mr. Trump's mind," he said.

Kazuhiro Maeshima, a professor at Sophia University, said Japan would not be able to rely on the United States any longer when designing its Indo-Pacific security policy unless Washington shows clear commitment to the defense of Taiwan.

"If Mr. Trump wins, an enormous challenge would await Japan" which would make it necessary to be strident in convincing his administration of the worth of the bilateral alliance, said Maeshima, a specialist in American politics and foreign policy.

Maeshima added Japan should "stress that it has done as much as possible" to strengthen the alliance and emphasize the significance of its recent policy maneuvers such as revising its key security policy documents and relaxing regulations on defense equipment exports.

In late 2022, Prime Minister Fumio Kishida's government pledged to obtain "counterstrike capabilities" to destroy targets in enemy territory, and almost double Japan's annual defense spending to 2 percent of its gross domestic product in five years in the revised National Security Strategy.

The government also lifted a ban on exporting domestically-produced, foreign-licensed lethal weapons to countries where licensers are based, by amending stringent arms export rules in December.

As the first instance of the eased regulations coming into action, Tokyo was quick to decide to provide the United States with U.S.-developed Patriot surface-to-air guided missiles made in Japan following a request from Washington.

Meanwhile, Tatsuhiko Yoshizaki, chief economist at the Sojitz Research Institute, said Japan can learn from its past "successful experiences" seen under the administration of former Prime Minister Shinzo Abe.

Abe, Japan's longest-serving prime minister who led the nation for one year from 2006 and again from 2012 until 2020, built a strong personal relationship with Trump. He was fatally shot during an election campaign speech in western Japan in July 2022.

Yoshizaki, well-versed in U.S. and international economic and political issues, said Abe managed to keep the Japan-U.S. alliance stable "because he explained its importance from the viewpoint of its cost-effectiveness," instead of principles such as the rule of law, when he met Trump.

For Japan, "Mr. Abe's approach should be helpful" in managing a second Trump term, he added.

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