"You can't ever get used to that sound," said Kazuyuki Tsuchiya, 72, who runs a small village inn on Hokkaido, the northernmost island of Japan. "It makes me feel so scared."

Over the course of the year, North Korea's missile provocations have become so frequent — 23 weapons tests since January, including four last week — that much of the public had ceased to pay attention. But Tuesday's flyover, with alarm bells rousing residents from their sleep, reminded them of the rogue nuclear threat in a region already unsettled by China's recent military drills near Taiwan.

Similar alarms sounded in Japan in 2017, a year when Kim Jong-un, the leader of North Korea, seemed intent on conflict. But the international landscape has changed considerably since then. A less mercurial president is in the White House, and the world is preoccupied by Russia's war in Ukraine, with President Vladimir V. Putin issuing a veiled threat to use tactical nuclear weapons. The global economy is struggling with energy shortages, inflation and the effects of a long coronavirus pandemic. Both China and Russia are less likely to cooperate with the United Nations on sanctions.