Several years ago, while making the rounds among Japanese defense officials, I was told that they viewed Northeast Asia as “a single operational theater.” As a proponent of a more prominent role for Japan in regional security affairs — and closer coordination and cooperation between Tokyo and Seoul in particular — that was a welcome and long overdue shift in thinking. It implied that Japan had to be involved in a Korean Peninsula contingency and that it couldn’t be shrugged off as unconnected to the nation’s security.

My confidence was quickly battered. A former senior U.S. defense official dismissed it, saying “I don’t know what that means.”

I’ve been revisiting those conversations in the wake of reports — almost completely missed in the press here and in the U.S. — that Japanese Defense Minister Gen Nakatani proposed a “one-theater” approach to U.S. Defense Secretary Pete Hegseth during their meeting in Tokyo at the end of March.