North Korea warned this week that it was strengthening its “nuclear war deterrence.” Experts don’t know what that means, but they are worried. Given North Korean leader Kim Jong Un’s promise to develop a new strategic weapon if the United States did not build a new relationship with his country, concern is justified. Japan should be especially worried, not just because it has bitter, longstanding issues with North Korea, but because this country is on the top of Pyongyang’s target list.

Kim declared last year that U.S. President Donald Trump had until the end of 2019 to make a “bold decision” to end his country’s “hostile policy” toward North Korea. Trump made historical and unprecedented gestures to Kim but the two men proved unable, even after two summits and, according to Trump, “falling in love” as a result of Kim’s “beautiful letters,” to go beyond vague promises of denuclearization.

The new year came and went without any shift in U.S. policy — it continues to demand that North Korea give up its nuclear weapons and maintains sanctions to encourage it to do so — and security planners have been waiting for Kim’s threat to take shape. North Korea has maintained its self-imposed moratorium on nuclear and long-range missile tests, but it has conducted 18 tests of short-range missiles and rockets since May of last year; five rounds have occurred in 2020, and the country set a record for the most tests in a single month (nine) earlier this year.