For both nations, with volatile North Korea on their doorstep, defense is of the utmost priority and each leader's congratulatory message hinted at that.
Japanese Prime Minister Shinzo Abe told Trump on Wednesday that Tokyo and Washington were "unshakeable allies," adding that stability in Asia-Pacific was crucial to peace and prosperity in the U.S. Abe planned to meet Trump in New York on Nov. 17, Reuters reported on Thursday.
South Korea's President Park Geun-hye said she hoped Washington would continue to cooperate with her country to address pending issues, including North Korea.
"South Korea and Japan are particularly unsettled by Trump's advocacy for removing all U.S. troops from Asia and Europe if the host nations did not pay 100 percent of their costs," explained Bruce Klingner, senior research fellow for Northeast Asia at The Heritage Foundation.
Should Trump deliver on that threat, it could embolden Seoul to risk China's ire by deploying the THAAD ballistic missile defense system, Klingner continued. South Korea had agreed with Washington to host a U.S. anti-missile defense system, known the Terminal High Altitude Area Defense (THAAD), to counter North Korea, but Beijing and Moscow are against the idea, calling THAAD a regional security threat.
For now, Trump has said he will maintain firm security commitments to Seoul, according to Yonhap News.
Tokyo, meanwhile, would need to increase spending to compensate for reduced U.S. troops, warned Guo. But greater defense outlays—already at record levels—would expand Japan's chronic budget deficit and add to its already massive debt pile, he noted.