War in the Pacific

I've got friends living in Yokohama, Japan and they tell me the US Navy base at Yokosuka is the busiest they've ever seen it. Also extremely busy are the Kanagawa area US Naval Air Facilities. Planes are flying in 24 hours a day, 7 days a week. Locals are complaining of the noise. Bear in mind all the various crises over the decades, but they say the bases have always just been ticking along despite that. Not now, now they're really ramping up. Based on this evidence I'd say the US is preparing for war and not just talking tough. Who will that war be with? North Korea is my suggestion and anyone else who takes their side.