Trump’s Talk of U.S. Troop Cuts Unnerves South Korea and Japan

“Across the waters in Japan, I think it’s going to be read very, very poorly and really make the Japanese anxious about what exactly are the U.S. commitments” in the region, said Jeffrey Hornung, a political scientist at the RAND Corporation.

Under Prime Minister Shinzo Abe, Japan has stepped up its own show of military force, and Mr. Abe has sought to revise the pacifist clause in the country’s Constitution. On Thursday, he released a video message calling for amending it to make explicit the legality of the country’s Self-Defense Forces, as Japan’s military, which has about 225,000 active members, is known.

On Friday Mr. Abe’s office called American forces “essential” for the security of the region.

If Mr. Trump were to succeed in pulling troops from the Korean Peninsula, it could embolden Mr. Abe to push through a constitutional change while citing the reduced American military presence in the region.

The Japanese public has long opposed any constitutional change and on Thursday, thousands of people protested the idea in Tokyo. But recent polls show opinion is increasingly divided.

Ichiro Fujisaki, a former Japanese ambassador to Washington, struck a moderate tone.

He said “the U.S. presence is more symbolic than really there to fight against North Korea,” given the strength of the South Korean military and the fact that North Korea’s missiles are a bigger threat than an actual invasion.

Mr. Fujisaki added that as long as the Trump administration consulted the Japanese and South Korean governments about its plans, “it’s not that big a concern.”

China has long wanted American troops to leave South Korea, and analysts there said a drawdown — or complete withdrawal — could drastically reshape the balance of power in the region.

“The end of American troops in South Korea may indicate the beginning of the dissolution of the U.S. alliance in the Asia-Pacific,” said Cheng Xiaohe, a professor of international relations at Renmin University in Beijing. “If the American alliance system was gone, China would be greatly relieved.”