North Korean dictator Kim Jong Un seems to be determined to keep U.S., South Korean and Japanese leaders off balance. It is a very dangerous game.

For a short while, it had seemed to some that Kim had at least paused in his saber rattling via missile launches. U.S. Secretary of State Rex Tillerson even remarked that Pyongyang appeared to be showing restraint.

Then, North Korea launched a missile on a test flight that took it over Japan. For the impact that had on the Japanese, consider how Americans would feel if anyone fired a military rocket over our heads.

This provocative missile launch probably was a reaction to joint U.S.-South Korean military exercises. Kim’s regime reacts with vicious rhetoric any time South Korea demonstrates its ability to defend itself.

What is puzzling is why North Korea fired a missile over Japan, something it has not done since 2009.

A reasonable conclusion is that Kim simply wanted to shake things up. It leads to speculation over what else he may do just because he can.

Clearly, that poses a challenge to President Donald Trump and other U.S. leaders — one like no U.S. leader has faced in recent memory. In short, Kim’s behavior means our nation must be very, very calm and calculated — but always ready for the worst.