Shinzo Abe, then the prime minister of Japan, succeeded in making friends with Mr. Trump through golf, entertainment and appealing to his vanity.

© Doug Mills/The New York Times

Western and Ukrainian officials have called the appearance of North Korean forces on the battlefield a major escalation.

© Yuri Kochetkov/EPA, via Shutterstock

American agencies have assessed that China dislikes the growing partnership between Russia and North Korea. The State Department has raised the troop issue with Chinese diplomats.

The Biden administration is struggling to halt cooperation among Russia, China, North Korea and Iran. It feels urgency over the wars in Ukraine and the Middle East while also aiming to protect Taiwan.